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	$106.99	6.343%	$113.7764	$113.78	$113.80	$113.80
Purchase #2	$243.56	6.397%	$259.1405	$259.14	$259.15	$259.10
Purchase #3	$174.73	8.483%	$189.5523	$189.55	$189.55	$189.60
Purchase #4	$34.86	6.810%	$37.234	$37.23	$37.25	$37.20
Purchase #5	$191.60	11.545%	$213.7202	$213.72	$213.70	$213.70
Purchase #6	$40.91	7.387%	$43.932	$43.93	$43.95	$43.90
Purchase #7	$174.25	5.233%	$183.3685	$183.37	$183.35	$183.40
7 purchase totals =	$966.90		$1,040.7239	$1,040.72	$1,040.75	$1,040.70