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	$157.87	6.160%	$167.5948	$167.59	$167.60	$167.60
Purchase #2	$158.86	7.576%	$170.8952	$170.90	$170.90	$170.90
Purchase #3	$55.90	6.379%	$59.4659	$59.47	$59.45	$59.50
Purchase #4	$249.32	8.367%	$270.1806	$270.18	$270.20	$270.20
Purchase #5	$67.95	4.640%	$71.1029	$71.10	$71.10	$71.10
Purchase #6	$66.60	13.392%	$75.5191	$75.52	$75.50	$75.50
Purchase #7	$112.51	13.767%	$127.9993	$128.00	$128.00	$128.00
7 purchase totals =	$869.01		$942.7578	$942.76	$942.75	$942.80