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	$182.98	9.489%	$200.343	$200.34	$200.35	$200.30
Purchase #2	$103.58	6.423%	$110.2329	$110.23	$110.25	$110.20
Purchase #3	$113.83	11.800%	$127.2619	$127.26	$127.25	$127.30
Purchase #4	$160.44	4.565%	$167.7641	$167.76	$167.75	$167.80
Purchase #5	$132.96	3.386%	$137.462	$137.46	$137.45	$137.50
Purchase #6	$50.41	6.582%	$53.728	$53.73	$53.75	$53.70
Purchase #7	$12.51	12.806%	$14.112	$14.11	$14.10	$14.10
7 purchase totals =	$756.71		$810.9039	$810.89	$810.90	$810.90