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	$184.61	6.164%	$195.9894	$195.99	$196.00	$196.00
Purchase #2	$169.79	11.837%	$189.888	$189.89	$189.90	$189.90
Purchase #3	$127.61	7.838%	$137.6121	$137.61	$137.60	$137.60
Purchase #4	$53.58	11.476%	$59.7288	$59.73	$59.75	$59.70
Purchase #5	$13.70	13.585%	$15.5611	$15.56	$15.55	$15.60
Purchase #6	$117.92	8.433%	$127.8642	$127.86	$127.85	$127.90
Purchase #7	$50.48	7.236%	$54.1327	$54.13	$54.15	$54.10
7 purchase totals =	$717.69		$780.7763	$780.77	$780.80	$780.80