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	$228.56	10.178%	$251.8228	$251.82	$251.80	$251.80
Purchase #2	$19.69	8.371%	$21.3382	$21.34	$21.35	$21.30
Purchase #3	$61.63	10.152%	$67.8867	$67.89	$67.90	$67.90
Purchase #4	$26.54	4.373%	$27.7006	$27.70	$27.70	$27.70
Purchase #5	$227.43	12.329%	$255.4698	$255.47	$255.45	$255.50
Purchase #6	$152.42	10.197%	$167.9623	$167.96	$167.95	$168.00
Purchase #7	$41.37	9.655%	$45.3643	$45.36	$45.35	$45.40
7 purchase totals =	$757.64		$837.5447	$837.54	$837.50	$837.60