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	$39.46	11.156%	$43.8622	$43.86	$43.85	$43.90
Purchase #2	$201.55	7.333%	$216.3297	$216.33	$216.35	$216.30
Purchase #3	$184.73	6.463%	$196.6691	$196.67	$196.65	$196.70
Purchase #4	$125.57	3.858%	$130.4145	$130.41	$130.40	$130.40
Purchase #5	$128.71	8.639%	$139.8293	$139.83	$139.85	$139.80
Purchase #6	$185.50	13.632%	$210.7874	$210.79	$210.80	$210.80
Purchase #7	$37.76	5.140%	$39.7009	$39.70	$39.70	$39.70
7 purchase totals =	$903.28		$977.5931	$977.59	$977.60	$977.60