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	$77.37	4.438%	$80.8037	$80.80	$80.80	$80.80
Purchase #2	$169.70	8.122%	$183.483	$183.48	$183.50	$183.50
Purchase #3	$75.46	10.235%	$83.1833	$83.18	$83.20	$83.20
Purchase #4	$145.43	4.125%	$151.429	$151.43	$151.45	$151.40
Purchase #5	$244.28	4.546%	$255.385	$255.39	$255.40	$255.40
Purchase #6	$130.88	5.850%	$138.5365	$138.54	$138.55	$138.50
Purchase #7	$201.30	5.572%	$212.5164	$212.52	$212.50	$212.50
7 purchase totals =	$1,044.42		$1,105.3369	$1,105.34	$1,105.40	$1,105.30