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	$173.63	6.702%	$185.2667	$185.27	$185.25	$185.30
Purchase #2	$247.88	6.190%	$263.2238	$263.22	$263.20	$263.20
Purchase #3	$102.77	13.320%	$116.459	$116.46	$116.45	$116.50
Purchase #4	$222.49	12.742%	$250.8397	$250.84	$250.85	$250.80
Purchase #5	$82.42	3.749%	$85.5099	$85.51	$85.50	$85.50
Purchase #6	$222.68	9.688%	$244.2532	$244.25	$244.25	$244.30
Purchase #7	$202.45	6.394%	$215.3947	$215.39	$215.40	$215.40
7 purchase totals =	$1,254.32		$1,360.9470	$1,360.94	$1,360.90	$1,361.00