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	$185.37	3.644%	$192.1249	$192.12	$192.10	$192.10
Purchase #2	$84.82	5.659%	$89.62	$89.62	$89.60	$89.60
Purchase #3	$175.86	11.802%	$196.615	$196.62	$196.60	$196.60
Purchase #4	$149.79	4.871%	$157.0863	$157.09	$157.10	$157.10
Purchase #5	$95.73	4.791%	$100.3164	$100.32	$100.30	$100.30
Purchase #6	$173.76	3.171%	$179.2699	$179.27	$179.25	$179.30
Purchase #7	$65.60	6.653%	$69.9644	$69.96	$69.95	$70.00
7 purchase totals =	$930.93		$984.9969	$985.00	$984.90	$985.00