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	$61.84	7.350%	$66.3852	$66.39	$66.40	$66.40
Purchase #2	$93.43	6.229%	$99.2498	$99.25	$99.25	$99.20
Purchase #3	$123.36	6.319%	$131.1551	$131.16	$131.15	$131.20
Purchase #4	$241.96	13.456%	$274.5181	$274.52	$274.50	$274.50
Purchase #5	$142.72	7.848%	$153.9207	$153.92	$153.90	$153.90
Purchase #6	$227.91	13.301%	$258.2243	$258.22	$258.20	$258.20
Purchase #7	$110.37	13.446%	$125.2104	$125.21	$125.20	$125.20
7 purchase totals =	$1,001.59		$1,108.6636	$1,108.67	$1,108.60	$1,108.60