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	$183.35	6.501%	$195.2696	$195.27	$195.25	$195.30
Purchase #2	$162.68	4.365%	$169.781	$169.78	$169.80	$169.80
Purchase #3	$209.89	11.349%	$233.7104	$233.71	$233.70	$233.70
Purchase #4	$29.90	10.655%	$33.0858	$33.09	$33.10	$33.10
Purchase #5	$208.82	9.517%	$228.6934	$228.69	$228.70	$228.70
Purchase #6	$37.25	5.729%	$39.3841	$39.38	$39.40	$39.40
Purchase #7	$29.80	5.608%	$31.4712	$31.47	$31.45	$31.50
7 purchase totals =	$861.69		$931.3955	$931.39	$931.40	$931.50