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	$215.45	12.561%	$242.5127	$242.51	$242.50	$242.50
Purchase #2	$141.72	12.586%	$159.5569	$159.56	$159.55	$159.60
Purchase #3	$168.86	10.661%	$186.8622	$186.86	$186.85	$186.90
Purchase #4	$104.89	3.451%	$108.5098	$108.51	$108.50	$108.50
Purchase #5	$58.47	4.873%	$61.3192	$61.32	$61.30	$61.30
Purchase #6	$210.59	11.562%	$234.9384	$234.94	$234.95	$234.90
Purchase #7	$181.59	4.224%	$189.2604	$189.26	$189.25	$189.30
7 purchase totals =	$1,081.57		$1,182.9596	$1,182.96	$1,182.90	$1,183.00