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	$139.47	6.743%	$148.8745	$148.87	$148.85	$148.90
Purchase #2	$168.61	11.836%	$188.5667	$188.57	$188.55	$188.60
Purchase #3	$227.84	11.284%	$253.5495	$253.55	$253.55	$253.50
Purchase #4	$52.47	6.257%	$55.753	$55.75	$55.75	$55.80
Purchase #5	$123.36	9.290%	$134.8201	$134.82	$134.80	$134.80
Purchase #6	$180.73	6.695%	$192.8299	$192.83	$192.85	$192.80
Purchase #7	$180.50	5.339%	$190.1369	$190.14	$190.15	$190.10
7 purchase totals =	$1,072.98		$1,164.5306	$1,164.53	$1,164.50	$1,164.50