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	$84.54	5.459%	$89.155	$89.16	$89.15	$89.20
Purchase #2	$194.86	7.344%	$209.1705	$209.17	$209.15	$209.20
Purchase #3	$182.96	11.375%	$203.7717	$203.77	$203.75	$203.80
Purchase #4	$30.46	5.675%	$32.1886	$32.19	$32.20	$32.20
Purchase #5	$238.32	6.442%	$253.6726	$253.67	$253.65	$253.70
Purchase #6	$28.44	9.614%	$31.1742	$31.17	$31.15	$31.20
Purchase #7	$62.72	5.658%	$66.2687	$66.27	$66.25	$66.30
7 purchase totals =	$822.30		$885.4013	$885.40	$885.30	$885.60