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	$167.97	10.263%	$185.2088	$185.21	$185.20	$185.20
Purchase #2	$89.36	4.530%	$93.408	$93.41	$93.40	$93.40
Purchase #3	$59.59	10.748%	$65.9947	$65.99	$66.00	$66.00
Purchase #4	$189.53	10.540%	$209.5065	$209.51	$209.50	$209.50
Purchase #5	$97.60	12.173%	$109.4808	$109.48	$109.50	$109.50
Purchase #6	$139.79	12.680%	$157.5154	$157.52	$157.50	$157.50
Purchase #7	$182.52	4.431%	$190.6075	$190.61	$190.60	$190.60
7 purchase totals =	$926.36		$1,011.7217	$1,011.73	$1,011.70	$1,011.70