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	$215.62	10.431%	$238.1113	$238.11	$238.10	$238.10
Purchase #2	$98.56	10.610%	$109.0172	$109.02	$109.00	$109.00
Purchase #3	$91.88	6.151%	$97.5315	$97.53	$97.55	$97.50
Purchase #4	$191.66	13.415%	$217.3712	$217.37	$217.35	$217.40
Purchase #5	$134.64	8.453%	$146.0211	$146.02	$146.00	$146.00
Purchase #6	$37.47	10.807%	$41.5194	$41.52	$41.50	$41.50
Purchase #7	$124.47	10.175%	$137.1348	$137.13	$137.15	$137.10
7 purchase totals =	$894.30		$986.7065	$986.70	$986.65	$986.60