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	$186.33	11.127%	$207.0629	$207.06	$207.05	$207.10
Purchase #2	$63.89	9.705%	$70.0905	$70.09	$70.10	$70.10
Purchase #3	$19.84	11.822%	$22.1855	$22.19	$22.20	$22.20
Purchase #4	$173.82	12.768%	$196.0133	$196.01	$196.00	$196.00
Purchase #5	$124.85	10.464%	$137.9143	$137.91	$137.90	$137.90
Purchase #6	$118.63	7.832%	$127.9211	$127.92	$127.90	$127.90
Purchase #7	$156.89	5.663%	$165.7747	$165.77	$165.75	$165.80
7 purchase totals =	$844.25		$926.9623	$926.95	$926.90	$927.00