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	$178.56	9.806%	$196.0696	$196.07	$196.05	$196.10
Purchase #2	$130.54	8.696%	$141.8918	$141.89	$141.90	$141.90
Purchase #3	$30.39	6.334%	$32.3149	$32.31	$32.30	$32.30
Purchase #4	$151.96	4.653%	$159.0307	$159.03	$159.05	$159.00
Purchase #5	$37.79	5.476%	$39.8594	$39.86	$39.85	$39.90
Purchase #6	$232.77	5.582%	$245.7632	$245.76	$245.75	$245.80
Purchase #7	$21.57	10.361%	$23.8049	$23.80	$23.80	$23.80
7 purchase totals =	$783.58		$838.7345	$838.72	$838.70	$838.80