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	$50.84	4.407%	$53.0805	$53.08	$53.10	$53.10
Purchase #2	$148.91	10.196%	$164.0929	$164.09	$164.10	$164.10
Purchase #3	$147.45	4.595%	$154.2253	$154.23	$154.25	$154.20
Purchase #4	$75.54	8.711%	$82.1203	$82.12	$82.10	$82.10
Purchase #5	$154.43	7.142%	$165.4594	$165.46	$165.45	$165.50
Purchase #6	$76.37	5.734%	$80.7491	$80.75	$80.75	$80.70
Purchase #7	$69.90	5.160%	$73.5068	$73.51	$73.50	$73.50
7 purchase totals =	$723.44		$773.2343	$773.24	$773.25	$773.20