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	$160.65	6.819%	$171.6047	$171.60	$171.60	$171.60
Purchase #2	$94.76	6.470%	$100.891	$100.89	$100.90	$100.90
Purchase #3	$85.46	8.858%	$93.03	$93.03	$93.05	$93.00
Purchase #4	$82.43	11.731%	$92.0999	$92.10	$92.10	$92.10
Purchase #5	$185.40	6.467%	$197.3898	$197.39	$197.40	$197.40
Purchase #6	$173.85	10.791%	$192.6102	$192.61	$192.60	$192.60
Purchase #7	$47.55	7.104%	$50.928	$50.93	$50.95	$50.90
7 purchase totals =	$830.10		$898.5536	$898.55	$898.60	$898.50