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	$98.43	4.815%	$103.1694	$103.17	$103.15	$103.20
Purchase #2	$224.96	9.145%	$245.5326	$245.53	$245.55	$245.50
Purchase #3	$57.26	3.410%	$59.2126	$59.21	$59.20	$59.20
Purchase #4	$238.70	3.785%	$247.7348	$247.73	$247.75	$247.70
Purchase #5	$172.41	4.166%	$179.5926	$179.59	$179.60	$179.60
Purchase #6	$237.56	11.400%	$264.6418	$264.64	$264.65	$264.60
Purchase #7	$59.96	3.667%	$62.1587	$62.16	$62.15	$62.20
7 purchase totals =	$1,089.28		$1,162.0425	$1,162.03	$1,162.05	$1,162.00