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	$93.25	7.525%	$100.2671	$100.27	$100.25	$100.30
Purchase #2	$41.42	6.748%	$44.215	$44.22	$44.20	$44.20
Purchase #3	$158.97	5.590%	$167.8564	$167.86	$167.85	$167.90
Purchase #4	$6.67	12.858%	$7.5276	$7.53	$7.55	$7.50
Purchase #5	$6.76	4.543%	$7.0671	$7.07	$7.05	$7.10
Purchase #6	$94.34	8.267%	$102.1391	$102.14	$102.15	$102.10
Purchase #7	$152.58	6.661%	$162.7434	$162.74	$162.75	$162.70
7 purchase totals =	$553.99		$591.8157	$591.83	$591.80	$591.80