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	$168.93	10.605%	$186.845	$186.85	$186.85	$186.80
Purchase #2	$211.53	6.545%	$225.3746	$225.37	$225.35	$225.40
Purchase #3	$79.56	5.170%	$83.6733	$83.67	$83.65	$83.70
Purchase #4	$172.74	13.758%	$196.5056	$196.51	$196.50	$196.50
Purchase #5	$147.37	11.846%	$164.8275	$164.83	$164.85	$164.80
Purchase #6	$166.34	3.391%	$171.9806	$171.98	$172.00	$172.00
Purchase #7	$242.85	4.404%	$253.5451	$253.55	$253.55	$253.50
7 purchase totals =	$1,189.32		$1,282.7517	$1,282.76	$1,282.75	$1,282.70