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	$72.67	7.477%	$78.1035	$78.10	$78.10	$78.10
Purchase #2	$244.50	8.327%	$264.8595	$264.86	$264.85	$264.90
Purchase #3	$243.77	10.439%	$269.2172	$269.22	$269.20	$269.20
Purchase #4	$111.32	13.425%	$126.2647	$126.26	$126.25	$126.30
Purchase #5	$218.27	6.861%	$233.2455	$233.25	$233.25	$233.20
Purchase #6	$18.67	3.781%	$19.3759	$19.38	$19.40	$19.40
Purchase #7	$224.45	13.557%	$254.8787	$254.88	$254.90	$254.90
7 purchase totals =	$1,133.65		$1,245.9450	$1,245.95	$1,245.95	$1,246.00