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	$64.47	12.362%	$72.4398	$72.44	$72.45	$72.40
Purchase #2	$223.46	10.768%	$247.5222	$247.52	$247.50	$247.50
Purchase #3	$57.83	10.351%	$63.816	$63.82	$63.80	$63.80
Purchase #4	$227.85	4.669%	$238.4883	$238.49	$238.50	$238.50
Purchase #5	$219.42	12.237%	$246.2704	$246.27	$246.25	$246.30
Purchase #6	$172.92	7.292%	$185.5293	$185.53	$185.55	$185.50
Purchase #7	$92.31	9.219%	$100.8201	$100.82	$100.80	$100.80
7 purchase totals =	$1,058.26		$1,154.8861	$1,154.89	$1,154.85	$1,154.80