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	$139.25	8.688%	$151.348	$151.35	$151.35	$151.30
Purchase #2	$72.50	6.822%	$77.446	$77.45	$77.45	$77.40
Purchase #3	$96.31	4.406%	$100.5534	$100.55	$100.55	$100.60
Purchase #4	$245.67	3.812%	$255.0349	$255.03	$255.05	$255.00
Purchase #5	$186.50	4.295%	$194.5102	$194.51	$194.50	$194.50
Purchase #6	$6.65	11.362%	$7.4056	$7.41	$7.40	$7.40
Purchase #7	$36.83	7.727%	$39.6759	$39.68	$39.70	$39.70
7 purchase totals =	$783.71		$825.9740	$825.98	$826.00	$825.90