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	$130.86	13.284%	$148.2434	$148.24	$148.25	$148.20
Purchase #2	$244.32	6.417%	$259.998	$260.00	$260.00	$260.00
Purchase #3	$101.99	7.132%	$109.2639	$109.26	$109.25	$109.30
Purchase #4	$93.89	10.792%	$104.0226	$104.02	$104.00	$104.00
Purchase #5	$104.57	7.103%	$111.9976	$112.00	$112.00	$112.00
Purchase #6	$194.78	13.615%	$221.2993	$221.30	$221.30	$221.30
Purchase #7	$150.46	12.249%	$168.8898	$168.89	$168.90	$168.90
7 purchase totals =	$1,020.87		$1,123.7146	$1,123.71	$1,123.70	$1,123.70