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	$41.44	3.452%	$42.8705	$42.87	$42.85	$42.90
Purchase #2	$242.80	10.176%	$267.5073	$267.51	$267.50	$267.50
Purchase #3	$144.47	10.353%	$159.427	$159.43	$159.45	$159.40
Purchase #4	$243.48	7.796%	$262.4617	$262.46	$262.45	$262.50
Purchase #5	$227.45	6.274%	$241.7202	$241.72	$241.70	$241.70
Purchase #6	$153.87	11.229%	$171.1481	$171.15	$171.15	$171.10
Purchase #7	$81.87	9.109%	$89.3275	$89.33	$89.35	$89.30
7 purchase totals =	$1,135.38		$1,234.4623	$1,234.47	$1,234.45	$1,234.40