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	$31.88	6.515%	$33.957	$33.96	$33.95	$34.00
Purchase #2	$113.46	6.836%	$121.2161	$121.22	$121.20	$121.20
Purchase #3	$175.77	11.784%	$196.4827	$196.48	$196.50	$196.50
Purchase #4	$18.83	12.299%	$21.1459	$21.15	$21.15	$21.10
Purchase #5	$63.43	11.325%	$70.6134	$70.61	$70.60	$70.60
Purchase #6	$120.97	5.286%	$127.3645	$127.36	$127.35	$127.40
Purchase #7	$200.29	11.399%	$223.1211	$223.12	$223.10	$223.10
7 purchase totals =	$724.63		$793.9007	$793.90	$793.85	$793.90