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	$69.72	3.590%	$72.2229	$72.22	$72.20	$72.20
Purchase #2	$182.55	4.620%	$190.9838	$190.98	$191.00	$191.00
Purchase #3	$55.51	4.271%	$57.8808	$57.88	$57.90	$57.90
Purchase #4	$207.61	10.836%	$230.1066	$230.11	$230.10	$230.10
Purchase #5	$25.83	11.840%	$28.8883	$28.89	$28.90	$28.90
Purchase #6	$13.33	10.810%	$14.771	$14.77	$14.75	$14.80
Purchase #7	$184.31	9.374%	$201.5872	$201.59	$201.60	$201.60
7 purchase totals =	$738.86		$796.4406	$796.44	$796.45	$796.50