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	$96.75	4.283%	$100.8938	$100.89	$100.90	$100.90
Purchase #2	$67.44	12.721%	$76.019	$76.02	$76.00	$76.00
Purchase #3	$22.88	3.717%	$23.7304	$23.73	$23.75	$23.70
Purchase #4	$171.93	7.822%	$185.3784	$185.38	$185.40	$185.40
Purchase #5	$140.62	4.376%	$146.7735	$146.77	$146.75	$146.80
Purchase #6	$202.55	7.579%	$217.9013	$217.90	$217.90	$217.90
Purchase #7	$222.72	12.600%	$250.7827	$250.78	$250.80	$250.80
7 purchase totals =	$924.89		$1,001.4791	$1,001.47	$1,001.50	$1,001.50