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	$89.87	5.193%	$94.5369	$94.54	$94.55	$94.50
Purchase #2	$93.69	8.305%	$101.471	$101.47	$101.45	$101.50
Purchase #3	$39.46	5.800%	$41.7487	$41.75	$41.75	$41.70
Purchase #4	$83.50	8.453%	$90.5583	$90.56	$90.55	$90.60
Purchase #5	$239.74	10.648%	$265.2675	$265.27	$265.25	$265.30
Purchase #6	$31.64	12.444%	$35.5773	$35.58	$35.60	$35.60
Purchase #7	$90.38	5.563%	$95.4078	$95.41	$95.40	$95.40
7 purchase totals =	$668.28		$724.5675	$724.58	$724.55	$724.60