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	$99.72	10.151%	$109.8426	$109.84	$109.85	$109.80
Purchase #2	$188.45	4.498%	$196.9265	$196.93	$196.95	$196.90
Purchase #3	$37.35	6.618%	$39.8218	$39.82	$39.80	$39.80
Purchase #4	$175.79	4.197%	$183.1679	$183.17	$183.15	$183.20
Purchase #5	$230.50	13.797%	$262.3021	$262.30	$262.30	$262.30
Purchase #6	$126.76	11.179%	$140.9305	$140.93	$140.95	$140.90
Purchase #7	$119.43	8.500%	$129.5816	$129.58	$129.60	$129.60
7 purchase totals =	$978.00		$1,062.5730	$1,062.57	$1,062.60	$1,062.50