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	$63.79	11.180%	$70.9217	$70.92	$70.90	$70.90
Purchase #2	$40.89	9.344%	$44.7108	$44.71	$44.70	$44.70
Purchase #3	$79.59	10.736%	$88.1348	$88.13	$88.15	$88.10
Purchase #4	$86.71	8.435%	$94.024	$94.02	$94.00	$94.00
Purchase #5	$192.63	4.165%	$200.653	$200.65	$200.65	$200.70
Purchase #6	$86.58	4.435%	$90.4198	$90.42	$90.40	$90.40
Purchase #7	$91.73	12.701%	$103.3806	$103.38	$103.40	$103.40
7 purchase totals =	$641.92		$692.2447	$692.23	$692.20	$692.20