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	$71.92	3.799%	$74.6522	$74.65	$74.65	$74.70
Purchase #2	$87.48	11.370%	$97.4265	$97.43	$97.45	$97.40
Purchase #3	$50.79	7.403%	$54.55	$54.55	$54.55	$54.60
Purchase #4	$194.46	7.768%	$209.5657	$209.57	$209.55	$209.60
Purchase #5	$55.28	7.513%	$59.4332	$59.43	$59.45	$59.40
Purchase #6	$123.28	11.560%	$137.5312	$137.53	$137.55	$137.50
Purchase #7	$191.64	13.789%	$218.0652	$218.07	$218.05	$218.10
7 purchase totals =	$774.85		$851.2240	$851.23	$851.25	$851.30