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	$76.61	4.192%	$79.8215	$79.82	$79.80	$79.80
Purchase #2	$187.61	3.302%	$193.8049	$193.80	$193.80	$193.80
Purchase #3	$198.58	6.708%	$211.9007	$211.90	$211.90	$211.90
Purchase #4	$43.31	7.587%	$46.5959	$46.60	$46.60	$46.60
Purchase #5	$224.31	11.641%	$250.4219	$250.42	$250.40	$250.40
Purchase #6	$214.51	13.246%	$242.924	$242.92	$242.90	$242.90
Purchase #7	$35.61	5.261%	$37.4834	$37.48	$37.50	$37.50
7 purchase totals =	$980.54		$1,062.9523	$1,062.94	$1,062.90	$1,062.90