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	$103.27	10.824%	$114.4479	$114.45	$114.45	$114.40
Purchase #2	$59.93	9.198%	$65.4424	$65.44	$65.45	$65.40
Purchase #3	$45.45	6.377%	$48.3483	$48.35	$48.35	$48.30
Purchase #4	$94.28	3.201%	$97.2979	$97.30	$97.30	$97.30
Purchase #5	$172.25	9.255%	$188.1917	$188.19	$188.20	$188.20
Purchase #6	$40.29	12.428%	$45.2972	$45.30	$45.30	$45.30
Purchase #7	$243.90	12.303%	$273.907	$273.91	$273.90	$273.90
7 purchase totals =	$759.37		$832.9324	$832.94	$832.95	$832.80