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	$137.29	3.170%	$141.6421	$141.64	$141.65	$141.60
Purchase #2	$43.98	3.779%	$45.642	$45.64	$45.65	$45.60
Purchase #3	$248.64	3.280%	$256.7954	$256.80	$256.80	$256.80
Purchase #4	$126.87	4.694%	$132.8253	$132.83	$132.85	$132.80
Purchase #5	$35.38	11.276%	$39.3694	$39.37	$39.35	$39.40
Purchase #6	$136.83	4.813%	$143.4156	$143.42	$143.40	$143.40
Purchase #7	$81.77	4.513%	$85.4603	$85.46	$85.45	$85.50
7 purchase totals =	$810.76		$845.1501	$845.16	$845.15	$845.10