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	$85.28	4.801%	$89.3743	$89.37	$89.35	$89.40
Purchase #2	$214.43	12.354%	$240.9207	$240.92	$240.90	$240.90
Purchase #3	$157.55	4.289%	$164.3073	$164.31	$164.30	$164.30
Purchase #4	$206.86	7.387%	$222.1407	$222.14	$222.15	$222.10
Purchase #5	$95.48	8.662%	$103.7505	$103.75	$103.75	$103.80
Purchase #6	$198.35	6.764%	$211.7664	$211.77	$211.75	$211.80
Purchase #7	$199.48	6.349%	$212.145	$212.15	$212.15	$212.10
7 purchase totals =	$1,157.43		$1,244.4049	$1,244.41	$1,244.35	$1,244.40