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	$108.33	13.867%	$123.3521	$123.35	$123.35	$123.40
Purchase #2	$163.91	3.413%	$169.5042	$169.50	$169.50	$169.50
Purchase #3	$36.77	11.383%	$40.9555	$40.96	$40.95	$41.00
Purchase #4	$226.69	7.514%	$243.7235	$243.72	$243.70	$243.70
Purchase #5	$70.88	12.309%	$79.6046	$79.60	$79.60	$79.60
Purchase #6	$215.38	11.222%	$239.5499	$239.55	$239.55	$239.50
Purchase #7	$159.94	4.283%	$166.7902	$166.79	$166.80	$166.80
7 purchase totals =	$981.90		$1,063.4800	$1,063.47	$1,063.45	$1,063.50