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	$147.98	11.788%	$165.4239	$165.42	$165.40	$165.40
Purchase #2	$67.25	11.606%	$75.055	$75.06	$75.05	$75.10
Purchase #3	$168.28	6.162%	$178.6494	$178.65	$178.65	$178.60
Purchase #4	$102.61	6.191%	$108.9626	$108.96	$108.95	$109.00
Purchase #5	$154.84	11.565%	$172.7472	$172.75	$172.75	$172.70
Purchase #6	$57.39	3.501%	$59.3992	$59.40	$59.40	$59.40
Purchase #7	$138.56	6.457%	$147.5068	$147.51	$147.50	$147.50
7 purchase totals =	$836.91		$907.7441	$907.75	$907.70	$907.70