Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$108.74	13.342%	$123.2481	$123.25	$123.25	$123.20
Purchase #2	$142.88	10.103%	$157.3152	$157.32	$157.30	$157.30
Purchase #3	$196.62	10.242%	$216.7578	$216.76	$216.75	$216.80
Purchase #4	$191.98	13.331%	$217.5729	$217.57	$217.55	$217.60
Purchase #5	$159.45	7.404%	$171.2557	$171.26	$171.25	$171.30
Purchase #6	$157.77	10.746%	$174.724	$174.72	$174.70	$174.70
Purchase #7	$139.63	11.131%	$155.1722	$155.17	$155.15	$155.20
7 purchase totals =	$1,097.07		$1,216.0459	$1,216.05	$1,215.95	$1,216.10