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	$97.56	12.215%	$109.477	$109.48	$109.50	$109.50
Purchase #2	$111.74	5.485%	$117.8689	$117.87	$117.85	$117.90
Purchase #3	$240.28	4.590%	$251.3089	$251.31	$251.30	$251.30
Purchase #4	$51.83	8.254%	$56.108	$56.11	$56.10	$56.10
Purchase #5	$160.42	11.587%	$179.0079	$179.01	$179.00	$179.00
Purchase #6	$205.52	6.397%	$218.6671	$218.67	$218.65	$218.70
Purchase #7	$210.95	3.231%	$217.7658	$217.77	$217.75	$217.80
7 purchase totals =	$1,078.30		$1,150.2036	$1,150.22	$1,150.15	$1,150.30