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	$99.52	8.789%	$108.2668	$108.27	$108.25	$108.30
Purchase #2	$98.91	10.638%	$109.432	$109.43	$109.45	$109.40
Purchase #3	$216.85	12.650%	$244.2815	$244.28	$244.30	$244.30
Purchase #4	$140.62	12.561%	$158.2833	$158.28	$158.30	$158.30
Purchase #5	$12.32	12.341%	$13.8404	$13.84	$13.85	$13.80
Purchase #6	$95.98	3.391%	$99.2347	$99.23	$99.25	$99.20
Purchase #7	$201.40	5.293%	$212.0601	$212.06	$212.05	$212.10
7 purchase totals =	$865.60		$945.3988	$945.39	$945.45	$945.40