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	$157.94	6.373%	$168.0055	$168.01	$168.00	$168.00
Purchase #2	$184.87	8.248%	$200.1181	$200.12	$200.10	$200.10
Purchase #3	$23.69	8.132%	$25.6165	$25.62	$25.60	$25.60
Purchase #4	$22.38	10.512%	$24.7326	$24.73	$24.75	$24.70
Purchase #5	$44.67	4.300%	$46.5908	$46.59	$46.60	$46.60
Purchase #6	$88.98	12.565%	$100.1603	$100.16	$100.15	$100.20
Purchase #7	$148.25	13.194%	$167.8101	$167.81	$167.80	$167.80
7 purchase totals =	$670.78		$733.0339	$733.04	$733.00	$733.00