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	$175.27	8.706%	$190.529	$190.53	$190.55	$190.50
Purchase #2	$40.37	12.217%	$45.302	$45.30	$45.30	$45.30
Purchase #3	$128.65	9.706%	$141.1368	$141.14	$141.15	$141.10
Purchase #4	$83.61	9.710%	$91.7285	$91.73	$91.75	$91.70
Purchase #5	$49.83	5.645%	$52.6429	$52.64	$52.65	$52.60
Purchase #6	$134.96	4.170%	$140.5878	$140.59	$140.60	$140.60
Purchase #7	$78.93	10.666%	$87.3487	$87.35	$87.35	$87.30
7 purchase totals =	$691.62		$749.2757	$749.28	$749.35	$749.10