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	$127.30	3.322%	$131.5289	$131.53	$131.55	$131.50
Purchase #2	$164.62	5.654%	$173.9276	$173.93	$173.95	$173.90
Purchase #3	$31.44	5.472%	$33.1604	$33.16	$33.15	$33.20
Purchase #4	$96.92	4.328%	$101.1147	$101.11	$101.10	$101.10
Purchase #5	$203.87	9.734%	$223.7147	$223.71	$223.70	$223.70
Purchase #6	$236.59	3.659%	$245.2468	$245.25	$245.25	$245.20
Purchase #7	$31.78	12.333%	$35.6994	$35.70	$35.70	$35.70
7 purchase totals =	$892.52		$944.3925	$944.39	$944.40	$944.30