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	$233.89	13.268%	$264.9225	$264.92	$264.90	$264.90
Purchase #2	$56.86	7.171%	$60.9374	$60.94	$60.95	$60.90
Purchase #3	$166.58	9.822%	$182.9415	$182.94	$182.95	$182.90
Purchase #4	$59.39	13.682%	$67.5157	$67.52	$67.50	$67.50
Purchase #5	$183.53	3.565%	$190.0728	$190.07	$190.05	$190.10
Purchase #6	$92.74	4.696%	$97.0951	$97.10	$97.10	$97.10
Purchase #7	$247.34	10.539%	$273.4072	$273.41	$273.40	$273.40
7 purchase totals =	$1,040.33		$1,136.8922	$1,136.90	$1,136.85	$1,136.80