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	$187.89	11.584%	$209.6552	$209.66	$209.65	$209.70
Purchase #2	$59.36	3.475%	$61.4228	$61.42	$61.40	$61.40
Purchase #3	$94.38	7.375%	$101.3405	$101.34	$101.35	$101.30
Purchase #4	$85.77	4.699%	$89.8003	$89.80	$89.80	$89.80
Purchase #5	$236.86	4.639%	$247.8479	$247.85	$247.85	$247.80
Purchase #6	$35.64	4.472%	$37.2338	$37.23	$37.25	$37.20
Purchase #7	$19.43	9.710%	$21.3167	$21.32	$21.30	$21.30
7 purchase totals =	$719.33		$768.6172	$768.62	$768.60	$768.50