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	$177.53	12.341%	$199.439	$199.44	$199.45	$199.40
Purchase #2	$248.40	7.606%	$267.2933	$267.29	$267.30	$267.30
Purchase #3	$39.43	7.274%	$42.2981	$42.30	$42.30	$42.30
Purchase #4	$114.83	9.253%	$125.4552	$125.46	$125.45	$125.50
Purchase #5	$250.76	5.655%	$264.9405	$264.94	$264.95	$264.90
Purchase #6	$50.33	10.845%	$55.7883	$55.79	$55.80	$55.80
Purchase #7	$57.43	4.568%	$60.0534	$60.05	$60.05	$60.10
7 purchase totals =	$938.71		$1,015.2678	$1,015.27	$1,015.30	$1,015.30