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	$85.66	7.314%	$91.9252	$91.93	$91.95	$91.90
Purchase #2	$92.55	11.163%	$102.8814	$102.88	$102.90	$102.90
Purchase #3	$197.34	3.386%	$204.0219	$204.02	$204.00	$204.00
Purchase #4	$132.78	9.713%	$145.6769	$145.68	$145.70	$145.70
Purchase #5	$203.88	12.401%	$229.1632	$229.16	$229.15	$229.20
Purchase #6	$163.43	3.113%	$168.5176	$168.52	$168.50	$168.50
Purchase #7	$55.29	11.287%	$61.5306	$61.53	$61.55	$61.50
7 purchase totals =	$930.93		$1,003.7168	$1,003.72	$1,003.75	$1,003.70