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	$88.87	13.247%	$100.6426	$100.64	$100.65	$100.60
Purchase #2	$168.88	13.539%	$191.7447	$191.74	$191.75	$191.70
Purchase #3	$11.27	4.594%	$11.7877	$11.79	$11.80	$11.80
Purchase #4	$112.56	11.575%	$125.5888	$125.59	$125.60	$125.60
Purchase #5	$22.70	10.664%	$25.1207	$25.12	$25.10	$25.10
Purchase #6	$246.56	11.872%	$275.8316	$275.83	$275.85	$275.80
Purchase #7	$242.87	11.401%	$270.5596	$270.56	$270.55	$270.60
7 purchase totals =	$893.71		$1,001.2757	$1,001.27	$1,001.30	$1,001.20