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	$173.38	7.600%	$186.5569	$186.56	$186.55	$186.60
Purchase #2	$210.67	13.521%	$239.1547	$239.15	$239.15	$239.20
Purchase #3	$164.88	9.104%	$179.8907	$179.89	$179.90	$179.90
Purchase #4	$198.38	9.790%	$217.8014	$217.80	$217.80	$217.80
Purchase #5	$87.47	3.483%	$90.5166	$90.52	$90.50	$90.50
Purchase #6	$63.26	13.723%	$71.9412	$71.94	$71.95	$71.90
Purchase #7	$137.47	7.205%	$147.3747	$147.37	$147.35	$147.40
7 purchase totals =	$1,035.51		$1,133.2362	$1,133.23	$1,133.20	$1,133.30