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	$92.88	9.726%	$101.9135	$101.91	$101.90	$101.90
Purchase #2	$191.99	10.224%	$211.6191	$211.62	$211.60	$211.60
Purchase #3	$130.74	13.135%	$147.9127	$147.91	$147.90	$147.90
Purchase #4	$159.98	8.534%	$173.6327	$173.63	$173.65	$173.60
Purchase #5	$127.82	3.343%	$132.093	$132.09	$132.10	$132.10
Purchase #6	$71.89	6.354%	$76.4579	$76.46	$76.45	$76.50
Purchase #7	$229.54	11.774%	$256.566	$256.57	$256.55	$256.60
7 purchase totals =	$1,004.84		$1,100.1949	$1,100.19	$1,100.15	$1,100.20