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	$133.36	5.813%	$141.1122	$141.11	$141.10	$141.10
Purchase #2	$242.77	4.539%	$253.7893	$253.79	$253.80	$253.80
Purchase #3	$39.38	10.518%	$43.522	$43.52	$43.50	$43.50
Purchase #4	$114.89	11.716%	$128.3505	$128.35	$128.35	$128.40
Purchase #5	$206.45	12.359%	$231.9652	$231.97	$231.95	$232.00
Purchase #6	$95.90	8.810%	$104.3488	$104.35	$104.35	$104.30
Purchase #7	$223.47	6.659%	$238.3509	$238.35	$238.35	$238.40
7 purchase totals =	$1,056.22		$1,141.4389	$1,141.44	$1,141.40	$1,141.50