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	$91.69	9.207%	$100.1319	$100.13	$100.15	$100.10
Purchase #2	$206.29	7.861%	$222.5065	$222.51	$222.50	$222.50
Purchase #3	$215.89	13.514%	$245.0654	$245.07	$245.05	$245.10
Purchase #4	$238.35	13.572%	$270.6989	$270.70	$270.70	$270.70
Purchase #5	$149.39	10.859%	$165.6123	$165.61	$165.60	$165.60
Purchase #6	$171.95	8.242%	$186.1221	$186.12	$186.10	$186.10
Purchase #7	$216.29	9.237%	$236.2687	$236.27	$236.25	$236.30
7 purchase totals =	$1,289.85		$1,426.4058	$1,426.41	$1,426.35	$1,426.40