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	$233.92	10.629%	$258.7834	$258.78	$258.80	$258.80
Purchase #2	$58.98	11.663%	$65.8588	$65.86	$65.85	$65.90
Purchase #3	$121.50	5.256%	$127.886	$127.89	$127.90	$127.90
Purchase #4	$160.80	6.437%	$171.1507	$171.15	$171.15	$171.20
Purchase #5	$233.49	4.292%	$243.5114	$243.51	$243.50	$243.50
Purchase #6	$138.78	11.165%	$154.2748	$154.27	$154.25	$154.30
Purchase #7	$28.98	12.347%	$32.5582	$32.56	$32.55	$32.60
7 purchase totals =	$976.45		$1,054.0233	$1,054.02	$1,054.00	$1,054.20