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	$57.74	3.339%	$59.6679	$59.67	$59.65	$59.70
Purchase #2	$46.67	8.246%	$50.5184	$50.52	$50.50	$50.50
Purchase #3	$195.59	3.190%	$201.8293	$201.83	$201.85	$201.80
Purchase #4	$144.74	4.850%	$151.7599	$151.76	$151.75	$151.80
Purchase #5	$227.48	9.673%	$249.4841	$249.48	$249.50	$249.50
Purchase #6	$86.76	6.655%	$92.5339	$92.53	$92.55	$92.50
Purchase #7	$61.35	4.517%	$64.1212	$64.12	$64.10	$64.10
7 purchase totals =	$820.33		$869.9147	$869.91	$869.90	$869.90