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	$110.37	4.296%	$115.1115	$115.11	$115.10	$115.10
Purchase #2	$120.42	5.485%	$127.025	$127.03	$127.05	$127.00
Purchase #3	$17.93	5.571%	$18.9289	$18.93	$18.95	$18.90
Purchase #4	$200.42	11.281%	$223.0294	$223.03	$223.05	$223.00
Purchase #5	$193.50	11.681%	$216.1027	$216.10	$216.10	$216.10
Purchase #6	$32.83	13.586%	$37.2903	$37.29	$37.30	$37.30
Purchase #7	$239.99	7.846%	$258.8196	$258.82	$258.80	$258.80
7 purchase totals =	$915.46		$996.3074	$996.31	$996.35	$996.20