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	$125.28	5.171%	$131.7582	$131.76	$131.75	$131.80
Purchase #2	$187.51	9.516%	$205.3535	$205.35	$205.35	$205.40
Purchase #3	$106.63	11.129%	$118.4969	$118.50	$118.50	$118.50
Purchase #4	$170.92	11.217%	$190.0921	$190.09	$190.10	$190.10
Purchase #5	$160.75	12.205%	$180.3695	$180.37	$180.35	$180.40
Purchase #6	$69.60	12.741%	$78.4677	$78.47	$78.45	$78.50
Purchase #7	$139.48	7.546%	$150.0052	$150.01	$150.00	$150.00
7 purchase totals =	$960.17		$1,054.5431	$1,054.55	$1,054.50	$1,054.70