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	$77.32	4.281%	$80.6301	$80.63	$80.65	$80.60
Purchase #2	$86.94	8.554%	$94.3768	$94.38	$94.40	$94.40
Purchase #3	$54.48	9.274%	$59.5325	$59.53	$59.55	$59.50
Purchase #4	$61.76	13.305%	$69.9772	$69.98	$70.00	$70.00
Purchase #5	$188.78	9.309%	$206.3535	$206.35	$206.35	$206.40
Purchase #6	$56.69	9.279%	$61.9503	$61.95	$61.95	$62.00
Purchase #7	$140.63	7.815%	$151.6202	$151.62	$151.60	$151.60
7 purchase totals =	$666.60		$724.4406	$724.44	$724.50	$724.50