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	$243.88	10.682%	$269.9313	$269.93	$269.95	$269.90
Purchase #2	$247.73	6.762%	$264.4815	$264.48	$264.50	$264.50
Purchase #3	$160.36	6.727%	$171.1474	$171.15	$171.15	$171.10
Purchase #4	$248.57	4.865%	$260.6629	$260.66	$260.65	$260.70
Purchase #5	$135.35	7.512%	$145.5175	$145.52	$145.50	$145.50
Purchase #6	$190.81	5.141%	$200.6195	$200.62	$200.60	$200.60
Purchase #7	$164.69	13.260%	$186.5279	$186.53	$186.55	$186.50
7 purchase totals =	$1,391.39		$1,498.8880	$1,498.89	$1,498.90	$1,498.80