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	$113.85	11.647%	$127.1101	$127.11	$127.10	$127.10
Purchase #2	$64.47	4.577%	$67.4208	$67.42	$67.40	$67.40
Purchase #3	$190.55	5.365%	$200.773	$200.77	$200.75	$200.80
Purchase #4	$206.82	11.362%	$230.3189	$230.32	$230.30	$230.30
Purchase #5	$236.95	10.486%	$261.7966	$261.80	$261.80	$261.80
Purchase #6	$235.48	11.229%	$261.922	$261.92	$261.90	$261.90
Purchase #7	$90.48	8.113%	$97.8206	$97.82	$97.80	$97.80
7 purchase totals =	$1,138.60		$1,247.1620	$1,247.16	$1,247.05	$1,247.10