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	$126.92	5.302%	$133.6493	$133.65	$133.65	$133.60
Purchase #2	$208.82	5.234%	$219.7496	$219.75	$219.75	$219.70
Purchase #3	$125.73	9.297%	$137.4191	$137.42	$137.40	$137.40
Purchase #4	$10.46	12.801%	$11.799	$11.80	$11.80	$11.80
Purchase #5	$84.55	5.263%	$88.9999	$89.00	$89.00	$89.00
Purchase #6	$86.33	4.701%	$90.3884	$90.39	$90.40	$90.40
Purchase #7	$155.38	12.269%	$174.4436	$174.44	$174.45	$174.40
7 purchase totals =	$798.19		$856.4489	$856.45	$856.45	$856.30