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	$172.87	13.694%	$196.5428	$196.54	$196.55	$196.50
Purchase #2	$130.68	8.187%	$141.3788	$141.38	$141.40	$141.40
Purchase #3	$84.51	8.159%	$91.4052	$91.41	$91.40	$91.40
Purchase #4	$45.96	7.596%	$49.4511	$49.45	$49.45	$49.50
Purchase #5	$25.56	5.511%	$26.9686	$26.97	$26.95	$27.00
Purchase #6	$150.33	5.313%	$158.317	$158.32	$158.30	$158.30
Purchase #7	$53.92	10.399%	$59.5271	$59.53	$59.55	$59.50
7 purchase totals =	$663.83		$723.5906	$723.60	$723.60	$723.60