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	$114.55	11.427%	$127.6396	$127.64	$127.65	$127.60
Purchase #2	$106.61	6.290%	$113.3158	$113.32	$113.30	$113.30
Purchase #3	$239.96	5.567%	$253.3186	$253.32	$253.30	$253.30
Purchase #4	$162.84	3.446%	$168.4515	$168.45	$168.45	$168.50
Purchase #5	$95.91	8.576%	$104.1352	$104.14	$104.15	$104.10
Purchase #6	$149.56	11.554%	$166.8402	$166.84	$166.85	$166.80
Purchase #7	$69.86	5.139%	$73.4501	$73.45	$73.45	$73.50
7 purchase totals =	$939.29		$1,007.1510	$1,007.16	$1,007.15	$1,007.10