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	$157.49	6.631%	$167.9332	$167.93	$167.95	$167.90
Purchase #2	$51.34	8.218%	$55.5591	$55.56	$55.55	$55.60
Purchase #3	$102.88	8.656%	$111.7853	$111.79	$111.80	$111.80
Purchase #4	$133.52	10.797%	$147.9362	$147.94	$147.95	$147.90
Purchase #5	$134.67	4.503%	$140.7342	$140.73	$140.75	$140.70
Purchase #6	$183.73	3.646%	$190.4288	$190.43	$190.45	$190.40
Purchase #7	$20.76	7.617%	$22.3413	$22.34	$22.35	$22.30
7 purchase totals =	$784.39		$836.7181	$836.72	$836.80	$836.60