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	$140.63	6.177%	$149.3167	$149.32	$149.30	$149.30
Purchase #2	$89.83	7.463%	$96.534	$96.53	$96.55	$96.50
Purchase #3	$126.87	4.435%	$132.4967	$132.50	$132.50	$132.50
Purchase #4	$169.71	11.864%	$189.8444	$189.84	$189.85	$189.80
Purchase #5	$122.38	8.836%	$133.1935	$133.19	$133.20	$133.20
Purchase #6	$175.46	12.185%	$196.8398	$196.84	$196.85	$196.80
Purchase #7	$157.84	9.127%	$172.2461	$172.25	$172.25	$172.20
7 purchase totals =	$982.72		$1,070.4712	$1,070.47	$1,070.50	$1,070.30