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	$248.97	10.147%	$274.233	$274.23	$274.25	$274.20
Purchase #2	$234.48	9.131%	$255.8904	$255.89	$255.90	$255.90
Purchase #3	$169.40	9.658%	$185.7607	$185.76	$185.75	$185.80
Purchase #4	$144.97	4.249%	$151.1298	$151.13	$151.15	$151.10
Purchase #5	$73.59	10.450%	$81.2802	$81.28	$81.30	$81.30
Purchase #6	$123.79	5.461%	$130.5502	$130.55	$130.55	$130.60
Purchase #7	$34.33	4.367%	$35.8292	$35.83	$35.85	$35.80
7 purchase totals =	$1,029.53		$1,114.6735	$1,114.67	$1,114.75	$1,114.70