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	$225.59	3.649%	$233.8218	$233.82	$233.80	$233.80
Purchase #2	$222.70	7.685%	$239.8145	$239.81	$239.80	$239.80
Purchase #3	$188.33	11.373%	$209.7488	$209.75	$209.75	$209.70
Purchase #4	$55.49	6.535%	$59.1163	$59.12	$59.10	$59.10
Purchase #5	$145.98	13.505%	$165.6946	$165.69	$165.70	$165.70
Purchase #6	$118.46	5.124%	$124.5299	$124.53	$124.55	$124.50
Purchase #7	$63.95	10.855%	$70.8918	$70.89	$70.90	$70.90
7 purchase totals =	$1,020.50		$1,103.6177	$1,103.61	$1,103.60	$1,103.50