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	$196.53	4.354%	$205.0869	$205.09	$205.10	$205.10
Purchase #2	$18.28	13.570%	$20.7606	$20.76	$20.75	$20.80
Purchase #3	$30.73	9.526%	$33.6573	$33.66	$33.65	$33.70
Purchase #4	$58.89	4.164%	$61.3422	$61.34	$61.35	$61.30
Purchase #5	$120.25	4.561%	$125.7346	$125.73	$125.75	$125.70
Purchase #6	$10.40	4.376%	$10.8551	$10.86	$10.85	$10.90
Purchase #7	$78.85	5.474%	$83.1662	$83.17	$83.15	$83.20
7 purchase totals =	$513.93		$540.6029	$540.61	$540.60	$540.70