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	$70.69	7.654%	$76.1006	$76.10	$76.10	$76.10
Purchase #2	$187.83	13.337%	$212.8809	$212.88	$212.90	$212.90
Purchase #3	$7.45	9.600%	$8.1652	$8.17	$8.15	$8.20
Purchase #4	$182.96	7.538%	$196.7515	$196.75	$196.75	$196.80
Purchase #5	$248.38	6.592%	$264.7532	$264.75	$264.75	$264.80
Purchase #6	$247.56	13.682%	$281.4312	$281.43	$281.45	$281.40
Purchase #7	$96.36	4.215%	$100.4216	$100.42	$100.40	$100.40
7 purchase totals =	$1,041.23		$1,140.5042	$1,140.50	$1,140.50	$1,140.60