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	$210.43	3.778%	$218.38	$218.38	$218.40	$218.40
Purchase #2	$55.93	6.793%	$59.7293	$59.73	$59.75	$59.70
Purchase #3	$72.83	6.705%	$77.7133	$77.71	$77.70	$77.70
Purchase #4	$190.83	6.573%	$203.3733	$203.37	$203.35	$203.40
Purchase #5	$124.37	5.750%	$131.5213	$131.52	$131.50	$131.50
Purchase #6	$209.48	4.565%	$219.0428	$219.04	$219.05	$219.00
Purchase #7	$59.77	7.136%	$64.0352	$64.04	$64.05	$64.00
7 purchase totals =	$923.64		$973.7952	$973.79	$973.80	$973.70