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	$54.96	12.527%	$61.8448	$61.84	$61.85	$61.80
Purchase #2	$48.32	3.611%	$50.0648	$50.06	$50.05	$50.10
Purchase #3	$145.38	7.535%	$156.3344	$156.33	$156.35	$156.30
Purchase #4	$211.72	9.344%	$231.5031	$231.50	$231.50	$231.50
Purchase #5	$224.91	10.829%	$249.2655	$249.27	$249.25	$249.30
Purchase #6	$30.47	6.561%	$32.4691	$32.47	$32.45	$32.50
Purchase #7	$249.26	6.121%	$264.5172	$264.52	$264.50	$264.50
7 purchase totals =	$965.02		$1,045.9989	$1,045.99	$1,045.95	$1,046.00