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	$44.87	4.441%	$46.8627	$46.86	$46.85	$46.90
Purchase #2	$87.44	9.720%	$95.9392	$95.94	$95.95	$95.90
Purchase #3	$225.51	12.308%	$253.2658	$253.27	$253.25	$253.30
Purchase #4	$180.91	9.757%	$198.5614	$198.56	$198.55	$198.60
Purchase #5	$162.36	12.556%	$182.7459	$182.75	$182.75	$182.70
Purchase #6	$31.44	4.609%	$32.8891	$32.89	$32.90	$32.90
Purchase #7	$240.61	12.639%	$271.0207	$271.02	$271.00	$271.00
7 purchase totals =	$973.14		$1,081.2848	$1,081.29	$1,081.25	$1,081.30