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	$185.35	9.211%	$202.4226	$202.42	$202.40	$202.40
Purchase #2	$24.77	5.459%	$26.1222	$26.12	$26.10	$26.10
Purchase #3	$109.46	4.247%	$114.1088	$114.11	$114.10	$114.10
Purchase #4	$60.94	11.221%	$67.7781	$67.78	$67.80	$67.80
Purchase #5	$33.39	13.589%	$37.9274	$37.93	$37.95	$37.90
Purchase #6	$9.56	13.284%	$10.83	$10.83	$10.85	$10.80
Purchase #7	$38.37	3.259%	$39.6205	$39.62	$39.60	$39.60
7 purchase totals =	$461.84		$498.8096	$498.81	$498.80	$498.70