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	$158.99	5.557%	$167.8251	$167.83	$167.85	$167.80
Purchase #2	$76.39	9.313%	$83.5042	$83.50	$83.50	$83.50
Purchase #3	$141.59	11.446%	$157.7964	$157.80	$157.80	$157.80
Purchase #4	$162.87	6.162%	$172.906	$172.91	$172.90	$172.90
Purchase #5	$99.47	7.494%	$106.9243	$106.92	$106.90	$106.90
Purchase #6	$151.95	3.870%	$157.8305	$157.83	$157.85	$157.80
Purchase #7	$199.76	11.673%	$223.078	$223.08	$223.10	$223.10
7 purchase totals =	$991.02		$1,069.8645	$1,069.87	$1,069.90	$1,069.80