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	$173.31	10.125%	$190.8576	$190.86	$190.85	$190.90
Purchase #2	$232.87	3.404%	$240.7969	$240.80	$240.80	$240.80
Purchase #3	$88.37	4.753%	$92.5702	$92.57	$92.55	$92.60
Purchase #4	$115.41	10.706%	$127.7658	$127.77	$127.75	$127.80
Purchase #5	$71.62	11.209%	$79.6479	$79.65	$79.65	$79.60
Purchase #6	$29.85	9.705%	$32.7469	$32.75	$32.75	$32.70
Purchase #7	$171.87	11.437%	$191.5268	$191.53	$191.55	$191.50
7 purchase totals =	$883.30		$955.9121	$955.93	$955.90	$955.90