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	$171.98	9.575%	$188.4471	$188.45	$188.45	$188.40
Purchase #2	$85.45	5.230%	$89.919	$89.92	$89.90	$89.90
Purchase #3	$13.86	3.627%	$14.3627	$14.36	$14.35	$14.40
Purchase #4	$124.54	4.518%	$130.1667	$130.17	$130.15	$130.20
Purchase #5	$61.61	9.536%	$67.4851	$67.49	$67.50	$67.50
Purchase #6	$137.89	7.413%	$148.1118	$148.11	$148.10	$148.10
Purchase #7	$157.58	4.275%	$164.3165	$164.32	$164.30	$164.30
7 purchase totals =	$752.91		$802.8089	$802.82	$802.75	$802.80