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	$128.98	5.447%	$136.0055	$136.01	$136.00	$136.00
Purchase #2	$172.68	5.464%	$182.1152	$182.12	$182.10	$182.10
Purchase #3	$85.70	12.478%	$96.3936	$96.39	$96.40	$96.40
Purchase #4	$177.67	12.672%	$200.1843	$200.18	$200.20	$200.20
Purchase #5	$69.40	4.250%	$72.3495	$72.35	$72.35	$72.30
Purchase #6	$224.38	5.868%	$237.5466	$237.55	$237.55	$237.50
Purchase #7	$122.30	11.662%	$136.5626	$136.56	$136.55	$136.60
7 purchase totals =	$981.11		$1,061.1573	$1,061.16	$1,061.15	$1,061.10