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	$84.34	9.694%	$92.5159	$92.52	$92.50	$92.50
Purchase #2	$31.69	5.730%	$33.5058	$33.51	$33.50	$33.50
Purchase #3	$90.33	5.809%	$95.5773	$95.58	$95.60	$95.60
Purchase #4	$151.49	9.330%	$165.624	$165.62	$165.60	$165.60
Purchase #5	$30.51	5.725%	$32.2567	$32.26	$32.25	$32.30
Purchase #6	$196.63	6.107%	$208.6382	$208.64	$208.65	$208.60
Purchase #7	$240.80	12.241%	$270.2763	$270.28	$270.30	$270.30
7 purchase totals =	$825.79		$898.3942	$898.41	$898.40	$898.40