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	$114.64	5.693%	$121.1665	$121.17	$121.15	$121.20
Purchase #2	$20.41	5.739%	$21.5813	$21.58	$21.60	$21.60
Purchase #3	$199.36	3.447%	$206.2319	$206.23	$206.25	$206.20
Purchase #4	$200.89	10.817%	$222.6203	$222.62	$222.60	$222.60
Purchase #5	$216.99	3.178%	$223.8859	$223.89	$223.90	$223.90
Purchase #6	$118.66	8.410%	$128.6393	$128.64	$128.65	$128.60
Purchase #7	$224.78	6.203%	$238.7231	$238.72	$238.70	$238.70
7 purchase totals =	$1,095.73		$1,162.8483	$1,162.85	$1,162.85	$1,162.80