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	$221.32	3.123%	$228.2318	$228.23	$228.25	$228.20
Purchase #2	$71.86	12.259%	$80.6693	$80.67	$80.65	$80.70
Purchase #3	$247.78	12.445%	$278.6162	$278.62	$278.60	$278.60
Purchase #4	$111.89	7.666%	$120.4675	$120.47	$120.45	$120.50
Purchase #5	$123.54	4.591%	$129.2117	$129.21	$129.20	$129.20
Purchase #6	$231.67	6.130%	$245.8714	$245.87	$245.85	$245.90
Purchase #7	$56.33	9.186%	$61.5045	$61.50	$61.50	$61.50
7 purchase totals =	$1,064.39		$1,144.5724	$1,144.57	$1,144.50	$1,144.60