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	$112.41	7.283%	$120.5968	$120.60	$120.60	$120.60
Purchase #2	$236.74	11.539%	$264.0574	$264.06	$264.05	$264.10
Purchase #3	$39.80	7.766%	$42.8909	$42.89	$42.90	$42.90
Purchase #4	$210.52	12.489%	$236.8118	$236.81	$236.80	$236.80
Purchase #5	$162.81	10.421%	$179.7764	$179.78	$179.80	$179.80
Purchase #6	$143.83	4.686%	$150.5699	$150.57	$150.55	$150.60
Purchase #7	$135.98	4.595%	$142.2283	$142.23	$142.25	$142.20
7 purchase totals =	$1,042.09		$1,136.9315	$1,136.94	$1,136.95	$1,137.00