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	$100.95	9.493%	$110.5332	$110.53	$110.55	$110.50
Purchase #2	$96.71	9.317%	$105.7205	$105.72	$105.70	$105.70
Purchase #3	$197.33	7.790%	$212.702	$212.70	$212.70	$212.70
Purchase #4	$101.77	3.662%	$105.4968	$105.50	$105.50	$105.50
Purchase #5	$137.40	11.292%	$152.9152	$152.92	$152.90	$152.90
Purchase #6	$131.87	6.385%	$140.2899	$140.29	$140.30	$140.30
Purchase #7	$100.97	12.474%	$113.565	$113.57	$113.55	$113.60
7 purchase totals =	$867.00		$941.2226	$941.23	$941.20	$941.20