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	$66.67	9.146%	$72.7676	$72.77	$72.75	$72.80
Purchase #2	$112.46	13.145%	$127.2429	$127.24	$127.25	$127.20
Purchase #3	$127.62	12.699%	$143.8265	$143.83	$143.85	$143.80
Purchase #4	$14.92	8.783%	$16.2304	$16.23	$16.25	$16.20
Purchase #5	$188.27	13.676%	$214.0178	$214.02	$214.00	$214.00
Purchase #6	$70.84	10.684%	$78.4085	$78.41	$78.40	$78.40
Purchase #7	$203.74	9.573%	$223.244	$223.24	$223.25	$223.20
7 purchase totals =	$784.52		$875.7377	$875.74	$875.75	$875.60