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	$81.32	7.675%	$87.5613	$87.56	$87.55	$87.60
Purchase #2	$216.32	11.265%	$240.6884	$240.69	$240.70	$240.70
Purchase #3	$132.64	13.828%	$150.9815	$150.98	$151.00	$151.00
Purchase #4	$195.31	7.635%	$210.2219	$210.22	$210.20	$210.20
Purchase #5	$169.60	10.712%	$187.7676	$187.77	$187.75	$187.80
Purchase #6	$246.77	3.465%	$255.3206	$255.32	$255.30	$255.30
Purchase #7	$82.47	3.830%	$85.6286	$85.63	$85.65	$85.60
7 purchase totals =	$1,124.43		$1,218.1699	$1,218.17	$1,218.15	$1,218.20