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	$160.91	4.634%	$168.3666	$168.37	$168.35	$168.40
Purchase #2	$5.97	12.112%	$6.6931	$6.69	$6.70	$6.70
Purchase #3	$187.89	13.613%	$213.4675	$213.47	$213.45	$213.50
Purchase #4	$106.57	3.267%	$110.0516	$110.05	$110.05	$110.10
Purchase #5	$31.78	5.410%	$33.4993	$33.50	$33.50	$33.50
Purchase #6	$196.42	13.275%	$222.4948	$222.49	$222.50	$222.50
Purchase #7	$91.73	6.501%	$97.6934	$97.69	$97.70	$97.70
7 purchase totals =	$781.27		$852.2663	$852.26	$852.25	$852.40