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	$55.98	4.258%	$58.3636	$58.36	$58.35	$58.40
Purchase #2	$229.31	9.853%	$251.9039	$251.90	$251.90	$251.90
Purchase #3	$247.59	7.226%	$265.4809	$265.48	$265.50	$265.50
Purchase #4	$99.40	11.499%	$110.83	$110.83	$110.85	$110.80
Purchase #5	$37.91	13.353%	$42.9721	$42.97	$42.95	$43.00
Purchase #6	$226.88	12.658%	$255.5985	$255.60	$255.60	$255.60
Purchase #7	$119.68	9.785%	$131.3907	$131.39	$131.40	$131.40
7 purchase totals =	$1,016.75		$1,116.5397	$1,116.53	$1,116.55	$1,116.60