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	$215.98	10.332%	$238.2951	$238.30	$238.30	$238.30
Purchase #2	$190.68	5.140%	$200.481	$200.48	$200.50	$200.50
Purchase #3	$21.39	11.406%	$23.8297	$23.83	$23.85	$23.80
Purchase #4	$109.41	5.652%	$115.5939	$115.59	$115.60	$115.60
Purchase #5	$70.47	11.275%	$78.4155	$78.42	$78.40	$78.40
Purchase #6	$91.60	3.617%	$94.9132	$94.91	$94.90	$94.90
Purchase #7	$91.61	13.193%	$103.6961	$103.70	$103.70	$103.70
7 purchase totals =	$791.14		$855.2245	$855.23	$855.25	$855.20