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	$96.44	13.502%	$109.4613	$109.46	$109.45	$109.50
Purchase #2	$78.58	5.275%	$82.7251	$82.73	$82.75	$82.70
Purchase #3	$12.89	9.692%	$14.1393	$14.14	$14.15	$14.10
Purchase #4	$195.87	10.593%	$216.6185	$216.62	$216.60	$216.60
Purchase #5	$73.71	11.600%	$82.2604	$82.26	$82.25	$82.30
Purchase #6	$36.47	8.360%	$39.5189	$39.52	$39.50	$39.50
Purchase #7	$188.50	10.819%	$208.8938	$208.89	$208.90	$208.90
7 purchase totals =	$682.46		$753.6173	$753.62	$753.60	$753.60