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	$182.68	4.501%	$190.9024	$190.90	$190.90	$190.90
Purchase #2	$57.35	5.440%	$60.4698	$60.47	$60.45	$60.50
Purchase #3	$185.46	4.567%	$193.93	$193.93	$193.95	$193.90
Purchase #4	$48.53	11.712%	$54.2138	$54.21	$54.20	$54.20
Purchase #5	$228.45	9.370%	$249.8558	$249.86	$249.85	$249.90
Purchase #6	$228.94	9.537%	$250.774	$250.77	$250.75	$250.80
Purchase #7	$109.95	12.273%	$123.4442	$123.44	$123.45	$123.40
7 purchase totals =	$1,041.36		$1,123.5900	$1,123.58	$1,123.55	$1,123.60