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	$216.38	8.282%	$234.3006	$234.30	$234.30	$234.30
Purchase #2	$191.42	11.740%	$213.8927	$213.89	$213.90	$213.90
Purchase #3	$99.54	3.763%	$103.2857	$103.29	$103.30	$103.30
Purchase #4	$145.78	5.233%	$153.4087	$153.41	$153.40	$153.40
Purchase #5	$71.60	8.257%	$77.512	$77.51	$77.50	$77.50
Purchase #6	$11.50	10.304%	$12.685	$12.69	$12.70	$12.70
Purchase #7	$28.96	11.869%	$32.3973	$32.40	$32.40	$32.40
7 purchase totals =	$765.18		$827.4820	$827.49	$827.50	$827.50