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	$228.89	9.678%	$251.042	$251.04	$251.05	$251.00
Purchase #2	$76.83	9.141%	$83.853	$83.85	$83.85	$83.90
Purchase #3	$49.25	12.568%	$55.4397	$55.44	$55.45	$55.40
Purchase #4	$160.80	6.417%	$171.1185	$171.12	$171.10	$171.10
Purchase #5	$63.41	10.489%	$70.0611	$70.06	$70.05	$70.10
Purchase #6	$146.87	4.520%	$153.5085	$153.51	$153.50	$153.50
Purchase #7	$131.32	6.191%	$139.45	$139.45	$139.45	$139.50
7 purchase totals =	$857.37		$924.4728	$924.47	$924.45	$924.50