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	$61.47	10.410%	$67.869	$67.87	$67.85	$67.90
Purchase #2	$61.70	10.134%	$67.9527	$67.95	$67.95	$68.00
Purchase #3	$81.54	12.136%	$91.4357	$91.44	$91.45	$91.40
Purchase #4	$124.76	12.557%	$140.4261	$140.43	$140.45	$140.40
Purchase #5	$150.75	5.830%	$159.5387	$159.54	$159.55	$159.50
Purchase #6	$137.62	13.391%	$156.0487	$156.05	$156.05	$156.00
Purchase #7	$99.61	5.358%	$104.9471	$104.95	$104.95	$104.90
7 purchase totals =	$717.45		$788.2180	$788.23	$788.25	$788.10