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	$50.49	9.382%	$55.227	$55.23	$55.25	$55.20
Purchase #2	$77.26	11.444%	$86.1016	$86.10	$86.10	$86.10
Purchase #3	$184.75	3.655%	$191.5026	$191.50	$191.50	$191.50
Purchase #4	$183.44	13.532%	$208.2631	$208.26	$208.25	$208.30
Purchase #5	$206.83	9.795%	$227.089	$227.09	$227.10	$227.10
Purchase #6	$140.67	13.825%	$160.1176	$160.12	$160.10	$160.10
Purchase #7	$42.95	9.109%	$46.8623	$46.86	$46.85	$46.90
7 purchase totals =	$886.39		$975.1632	$975.16	$975.15	$975.20