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	$183.45	7.234%	$196.7208	$196.72	$196.70	$196.70
Purchase #2	$85.46	11.355%	$95.164	$95.16	$95.15	$95.20
Purchase #3	$157.60	11.491%	$175.7098	$175.71	$175.70	$175.70
Purchase #4	$209.48	8.460%	$227.202	$227.20	$227.20	$227.20
Purchase #5	$117.80	11.726%	$131.6132	$131.61	$131.60	$131.60
Purchase #6	$218.89	3.596%	$226.7613	$226.76	$226.75	$226.80
Purchase #7	$137.99	6.849%	$147.4409	$147.44	$147.45	$147.40
7 purchase totals =	$1,110.67		$1,200.6120	$1,200.60	$1,200.55	$1,200.60