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	$157.62	4.274%	$164.3567	$164.36	$164.35	$164.40
Purchase #2	$201.80	9.872%	$221.7217	$221.72	$221.70	$221.70
Purchase #3	$180.93	10.792%	$200.456	$200.46	$200.45	$200.50
Purchase #4	$207.78	3.779%	$215.632	$215.63	$215.65	$215.60
Purchase #5	$169.82	8.447%	$184.1647	$184.16	$184.15	$184.20
Purchase #6	$31.34	3.518%	$32.4425	$32.44	$32.45	$32.40
Purchase #7	$50.82	6.593%	$54.1706	$54.17	$54.15	$54.20
7 purchase totals =	$1,000.11		$1,072.9442	$1,072.94	$1,072.90	$1,073.00