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	$231.31	5.427%	$243.8632	$243.86	$243.85	$243.90
Purchase #2	$99.74	11.527%	$111.237	$111.24	$111.25	$111.20
Purchase #3	$80.47	10.822%	$89.1785	$89.18	$89.20	$89.20
Purchase #4	$211.84	4.214%	$220.7669	$220.77	$220.75	$220.80
Purchase #5	$162.91	3.592%	$168.7617	$168.76	$168.75	$168.80
Purchase #6	$37.74	7.322%	$40.5033	$40.50	$40.50	$40.50
Purchase #7	$18.37	7.515%	$19.7505	$19.75	$19.75	$19.80
7 purchase totals =	$842.38		$894.0611	$894.06	$894.05	$894.20