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	$123.49	7.400%	$132.6283	$132.63	$132.65	$132.60
Purchase #2	$53.64	7.574%	$57.7027	$57.70	$57.70	$57.70
Purchase #3	$83.30	11.219%	$92.6454	$92.65	$92.65	$92.60
Purchase #4	$95.32	8.574%	$103.4927	$103.49	$103.50	$103.50
Purchase #5	$247.69	11.349%	$275.8003	$275.80	$275.80	$275.80
Purchase #6	$42.92	12.637%	$48.3438	$48.34	$48.35	$48.30
Purchase #7	$153.94	7.465%	$165.4316	$165.43	$165.45	$165.40
7 purchase totals =	$800.30		$876.0448	$876.04	$876.10	$875.90