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	$36.59	11.793%	$40.9051	$40.91	$40.90	$40.90
Purchase #2	$165.83	6.142%	$176.0153	$176.02	$176.00	$176.00
Purchase #3	$144.78	12.179%	$162.4128	$162.41	$162.40	$162.40
Purchase #4	$24.86	9.568%	$27.2386	$27.24	$27.25	$27.20
Purchase #5	$222.28	13.744%	$252.8302	$252.83	$252.85	$252.80
Purchase #6	$145.72	5.793%	$154.1616	$154.16	$154.15	$154.20
Purchase #7	$197.33	7.681%	$212.4869	$212.49	$212.50	$212.50
7 purchase totals =	$937.39		$1,026.0505	$1,026.06	$1,026.05	$1,026.00