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	$83.66	3.207%	$86.343	$86.34	$86.35	$86.30
Purchase #2	$91.48	13.512%	$103.8408	$103.84	$103.85	$103.80
Purchase #3	$242.30	12.763%	$273.2247	$273.22	$273.20	$273.20
Purchase #4	$239.54	4.414%	$250.1133	$250.11	$250.10	$250.10
Purchase #5	$142.27	6.364%	$151.3241	$151.32	$151.30	$151.30
Purchase #6	$126.46	13.415%	$143.4246	$143.42	$143.40	$143.40
Purchase #7	$33.92	8.769%	$36.8944	$36.89	$36.90	$36.90
7 purchase totals =	$959.63		$1,045.1649	$1,045.14	$1,045.10	$1,045.00