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	$107.52	6.848%	$114.883	$114.88	$114.90	$114.90
Purchase #2	$37.99	12.157%	$42.6084	$42.61	$42.60	$42.60
Purchase #3	$197.48	6.449%	$210.2155	$210.22	$210.20	$210.20
Purchase #4	$13.93	10.619%	$15.4092	$15.41	$15.40	$15.40
Purchase #5	$185.60	3.338%	$191.7953	$191.80	$191.80	$191.80
Purchase #6	$152.34	10.823%	$168.8278	$168.83	$168.85	$168.80
Purchase #7	$215.90	3.344%	$223.1197	$223.12	$223.10	$223.10
7 purchase totals =	$910.76		$966.8589	$966.87	$966.85	$966.80