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	$149.90	11.792%	$167.5762	$167.58	$167.60	$167.60
Purchase #2	$119.40	6.547%	$127.2171	$127.22	$127.20	$127.20
Purchase #3	$226.68	9.453%	$248.1081	$248.11	$248.10	$248.10
Purchase #4	$155.70	6.468%	$165.7707	$165.77	$165.75	$165.80
Purchase #5	$162.39	5.767%	$171.755	$171.76	$171.75	$171.80
Purchase #6	$150.86	13.196%	$170.7675	$170.77	$170.75	$170.80
Purchase #7	$103.65	10.482%	$114.5146	$114.51	$114.50	$114.50
7 purchase totals =	$1,068.58		$1,165.7092	$1,165.72	$1,165.65	$1,165.80