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	$78.45	9.504%	$85.9059	$85.91	$85.90	$85.90
Purchase #2	$142.28	7.162%	$152.4701	$152.47	$152.45	$152.50
Purchase #3	$249.33	6.139%	$264.6364	$264.64	$264.65	$264.60
Purchase #4	$57.50	6.297%	$61.1208	$61.12	$61.10	$61.10
Purchase #5	$243.85	8.683%	$265.0235	$265.02	$265.00	$265.00
Purchase #6	$190.41	4.592%	$199.1536	$199.15	$199.15	$199.20
Purchase #7	$92.32	7.270%	$99.0317	$99.03	$99.05	$99.00
7 purchase totals =	$1,054.14		$1,127.3420	$1,127.34	$1,127.30	$1,127.30