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	$57.59	3.535%	$59.6258	$59.63	$59.65	$59.60
Purchase #2	$156.28	8.620%	$169.7513	$169.75	$169.75	$169.80
Purchase #3	$36.71	4.178%	$38.2437	$38.24	$38.25	$38.20
Purchase #4	$203.26	12.505%	$228.6777	$228.68	$228.70	$228.70
Purchase #5	$139.56	5.627%	$147.413	$147.41	$147.40	$147.40
Purchase #6	$28.67	11.824%	$32.0599	$32.06	$32.05	$32.10
Purchase #7	$77.54	3.836%	$80.5144	$80.51	$80.50	$80.50
7 purchase totals =	$699.61		$756.2858	$756.28	$756.30	$756.30