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	$156.64	3.438%	$162.0253	$162.03	$162.05	$162.00
Purchase #2	$212.25	10.217%	$233.9356	$233.94	$233.95	$233.90
Purchase #3	$45.55	7.711%	$49.0624	$49.06	$49.05	$49.10
Purchase #4	$52.51	12.859%	$59.2623	$59.26	$59.25	$59.30
Purchase #5	$70.65	11.690%	$78.909	$78.91	$78.90	$78.90
Purchase #6	$157.51	11.141%	$175.0582	$175.06	$175.05	$175.10
Purchase #7	$32.70	5.716%	$34.5691	$34.57	$34.55	$34.60
7 purchase totals =	$727.81		$792.8219	$792.83	$792.80	$792.90