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	$86.26	5.570%	$91.0647	$91.06	$91.05	$91.10
Purchase #2	$91.66	8.644%	$99.5831	$99.58	$99.60	$99.60
Purchase #3	$130.76	13.515%	$148.4322	$148.43	$148.45	$148.40
Purchase #4	$130.78	8.311%	$141.6491	$141.65	$141.65	$141.60
Purchase #5	$91.97	12.815%	$103.756	$103.76	$103.75	$103.80
Purchase #6	$34.39	8.447%	$37.2949	$37.29	$37.30	$37.30
Purchase #7	$243.99	4.338%	$254.5743	$254.57	$254.55	$254.60
7 purchase totals =	$809.81		$876.3543	$876.34	$876.35	$876.40