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	$39.29	4.213%	$40.9453	$40.95	$40.95	$40.90
Purchase #2	$234.64	4.151%	$244.3799	$244.38	$244.40	$244.40
Purchase #3	$153.61	11.860%	$171.8281	$171.83	$171.85	$171.80
Purchase #4	$190.75	4.816%	$199.9365	$199.94	$199.95	$199.90
Purchase #5	$212.40	4.819%	$222.6356	$222.64	$222.65	$222.60
Purchase #6	$221.76	8.621%	$240.8779	$240.88	$240.90	$240.90
Purchase #7	$158.44	10.719%	$175.4232	$175.42	$175.40	$175.40
7 purchase totals =	$1,210.89		$1,296.0265	$1,296.04	$1,296.10	$1,295.90