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	$159.87	13.117%	$180.8401	$180.84	$180.85	$180.80
Purchase #2	$145.98	3.103%	$150.5098	$150.51	$150.50	$150.50
Purchase #3	$19.78	13.140%	$22.3791	$22.38	$22.40	$22.40
Purchase #4	$41.69	9.612%	$45.6972	$45.70	$45.70	$45.70
Purchase #5	$169.49	9.384%	$185.3949	$185.39	$185.40	$185.40
Purchase #6	$39.80	4.871%	$41.7387	$41.74	$41.75	$41.70
Purchase #7	$245.70	9.268%	$268.4715	$268.47	$268.45	$268.50
7 purchase totals =	$822.31		$895.0313	$895.03	$895.05	$895.00