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	$92.25	11.655%	$103.0017	$103.00	$103.00	$103.00
Purchase #2	$51.30	11.830%	$57.3688	$57.37	$57.35	$57.40
Purchase #3	$85.34	12.317%	$95.8513	$95.85	$95.85	$95.90
Purchase #4	$206.56	11.515%	$230.3454	$230.35	$230.35	$230.30
Purchase #5	$221.97	13.632%	$252.229	$252.23	$252.25	$252.20
Purchase #6	$39.73	6.492%	$42.3093	$42.31	$42.30	$42.30
Purchase #7	$145.94	4.568%	$152.6065	$152.61	$152.60	$152.60
7 purchase totals =	$843.09		$933.7120	$933.72	$933.70	$933.70