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	$32.75	13.139%	$37.053	$37.05	$37.05	$37.10
Purchase #2	$106.38	5.342%	$112.0628	$112.06	$112.05	$112.10
Purchase #3	$179.97	4.214%	$187.5539	$187.55	$187.55	$187.60
Purchase #4	$101.78	9.741%	$111.6944	$111.69	$111.70	$111.70
Purchase #5	$213.66	9.774%	$234.5431	$234.54	$234.55	$234.50
Purchase #6	$175.47	8.344%	$190.1112	$190.11	$190.10	$190.10
Purchase #7	$51.56	9.276%	$56.3427	$56.34	$56.35	$56.30
7 purchase totals =	$861.57		$929.3611	$929.34	$929.35	$929.40