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	$65.89	13.159%	$74.5605	$74.56	$74.55	$74.60
Purchase #2	$102.80	4.753%	$107.6861	$107.69	$107.70	$107.70
Purchase #3	$151.48	13.473%	$171.8889	$171.89	$171.90	$171.90
Purchase #4	$201.31	5.119%	$211.6151	$211.62	$211.60	$211.60
Purchase #5	$214.67	7.558%	$230.8948	$230.89	$230.90	$230.90
Purchase #6	$162.60	5.501%	$171.5446	$171.54	$171.55	$171.50
Purchase #7	$172.62	10.797%	$191.2578	$191.26	$191.25	$191.30
7 purchase totals =	$1,071.37		$1,159.4478	$1,159.45	$1,159.45	$1,159.50