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	$94.83	11.629%	$105.8578	$105.86	$105.85	$105.90
Purchase #2	$9.65	11.703%	$10.7793	$10.78	$10.80	$10.80
Purchase #3	$53.61	10.276%	$59.119	$59.12	$59.10	$59.10
Purchase #4	$195.60	4.511%	$204.4235	$204.42	$204.40	$204.40
Purchase #5	$64.55	5.519%	$68.1125	$68.11	$68.10	$68.10
Purchase #6	$35.57	3.615%	$36.8559	$36.86	$36.85	$36.90
Purchase #7	$150.71	3.248%	$155.6051	$155.61	$155.60	$155.60
7 purchase totals =	$604.52		$640.7531	$640.76	$640.70	$640.80