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	$82.75	11.461%	$92.234	$92.23	$92.25	$92.20
Purchase #2	$80.89	3.808%	$83.9703	$83.97	$83.95	$84.00
Purchase #3	$209.40	12.559%	$235.6985	$235.70	$235.70	$235.70
Purchase #4	$53.73	3.364%	$55.5375	$55.54	$55.55	$55.50
Purchase #5	$95.86	10.515%	$105.9397	$105.94	$105.95	$105.90
Purchase #6	$103.43	12.543%	$116.4032	$116.40	$116.40	$116.40
Purchase #7	$53.44	11.482%	$59.576	$59.58	$59.60	$59.60
7 purchase totals =	$679.50		$749.3592	$749.36	$749.40	$749.30