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	$208.42	3.818%	$216.3775	$216.38	$216.40	$216.40
Purchase #2	$54.62	12.224%	$61.2967	$61.30	$61.30	$61.30
Purchase #3	$28.61	11.196%	$31.8132	$31.81	$31.80	$31.80
Purchase #4	$63.63	3.232%	$65.6865	$65.69	$65.70	$65.70
Purchase #5	$25.80	6.112%	$27.3769	$27.38	$27.40	$27.40
Purchase #6	$151.71	7.384%	$162.9123	$162.91	$162.90	$162.90
Purchase #7	$15.28	4.478%	$15.9642	$15.96	$15.95	$16.00
7 purchase totals =	$548.07		$581.4273	$581.43	$581.45	$581.50