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	$59.47	10.317%	$65.6055	$65.61	$65.60	$65.60
Purchase #2	$110.83	9.137%	$120.9565	$120.96	$120.95	$121.00
Purchase #3	$137.31	10.366%	$151.5436	$151.54	$151.55	$151.50
Purchase #4	$39.48	7.107%	$42.2858	$42.29	$42.30	$42.30
Purchase #5	$192.69	8.705%	$209.4637	$209.46	$209.45	$209.50
Purchase #6	$83.82	13.457%	$95.0997	$95.10	$95.10	$95.10
Purchase #7	$98.68	8.180%	$106.752	$106.75	$106.75	$106.80
7 purchase totals =	$722.28		$791.7068	$791.71	$791.70	$791.80