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	$97.37	3.822%	$101.0915	$101.09	$101.10	$101.10
Purchase #2	$168.34	4.418%	$175.7773	$175.78	$175.80	$175.80
Purchase #3	$131.81	9.626%	$144.498	$144.50	$144.50	$144.50
Purchase #4	$40.91	13.739%	$46.5306	$46.53	$46.55	$46.50
Purchase #5	$32.60	11.161%	$36.2385	$36.24	$36.25	$36.20
Purchase #6	$93.30	5.717%	$98.634	$98.63	$98.65	$98.60
Purchase #7	$60.25	7.457%	$64.7428	$64.74	$64.75	$64.70
7 purchase totals =	$624.58		$667.5127	$667.51	$667.60	$667.40