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	$239.51	7.234%	$256.8362	$256.84	$256.85	$256.80
Purchase #2	$32.74	8.441%	$35.5036	$35.50	$35.50	$35.50
Purchase #3	$133.69	11.151%	$148.5978	$148.60	$148.60	$148.60
Purchase #4	$173.25	9.471%	$189.6585	$189.66	$189.65	$189.70
Purchase #5	$72.42	11.165%	$80.5057	$80.51	$80.50	$80.50
Purchase #6	$96.86	6.812%	$103.4581	$103.46	$103.45	$103.50
Purchase #7	$250.68	12.460%	$281.9147	$281.91	$281.90	$281.90
7 purchase totals =	$999.15		$1,096.4746	$1,096.48	$1,096.45	$1,096.50