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	$105.78	6.318%	$112.4632	$112.46	$112.45	$112.50
Purchase #2	$67.90	3.381%	$70.1957	$70.20	$70.20	$70.20
Purchase #3	$179.79	5.250%	$189.229	$189.23	$189.25	$189.20
Purchase #4	$147.74	7.154%	$158.3093	$158.31	$158.30	$158.30
Purchase #5	$66.52	8.814%	$72.3831	$72.38	$72.40	$72.40
Purchase #6	$210.40	5.221%	$221.385	$221.39	$221.40	$221.40
Purchase #7	$142.73	5.251%	$150.2248	$150.22	$150.20	$150.20
7 purchase totals =	$920.86		$974.1901	$974.19	$974.20	$974.20