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	$183.55	4.484%	$191.7804	$191.78	$191.80	$191.80
Purchase #2	$155.47	9.128%	$169.6613	$169.66	$169.65	$169.70
Purchase #3	$150.66	6.485%	$160.4303	$160.43	$160.45	$160.40
Purchase #4	$98.71	12.707%	$111.2531	$111.25	$111.25	$111.30
Purchase #5	$114.78	10.806%	$127.1831	$127.18	$127.20	$127.20
Purchase #6	$121.36	6.741%	$129.5409	$129.54	$129.55	$129.50
Purchase #7	$156.32	8.614%	$169.7854	$169.79	$169.80	$169.80
7 purchase totals =	$980.85		$1,059.6345	$1,059.63	$1,059.70	$1,059.70