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	$43.55	3.549%	$45.0956	$45.10	$45.10	$45.10
Purchase #2	$97.89	6.391%	$104.1461	$104.15	$104.15	$104.10
Purchase #3	$172.39	7.687%	$185.6416	$185.64	$185.65	$185.60
Purchase #4	$59.63	4.284%	$62.1845	$62.18	$62.20	$62.20
Purchase #5	$121.49	8.768%	$132.1422	$132.14	$132.15	$132.10
Purchase #6	$105.73	5.446%	$111.4881	$111.49	$111.50	$111.50
Purchase #7	$98.93	11.704%	$110.5088	$110.51	$110.50	$110.50
7 purchase totals =	$699.61		$751.2069	$751.21	$751.25	$751.10