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	$58.94	10.181%	$64.9407	$64.94	$64.95	$64.90
Purchase #2	$171.48	12.467%	$192.8584	$192.86	$192.85	$192.90
Purchase #3	$247.90	10.115%	$272.9751	$272.98	$273.00	$273.00
Purchase #4	$110.87	11.823%	$123.9782	$123.98	$124.00	$124.00
Purchase #5	$54.75	8.467%	$59.3857	$59.39	$59.40	$59.40
Purchase #6	$56.29	10.701%	$62.3136	$62.31	$62.30	$62.30
Purchase #7	$221.34	5.294%	$233.0577	$233.06	$233.05	$233.10
7 purchase totals =	$921.57		$1,009.5094	$1,009.52	$1,009.55	$1,009.60