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	$37.69	10.822%	$41.7688	$41.77	$41.75	$41.80
Purchase #2	$235.37	4.262%	$245.4015	$245.40	$245.40	$245.40
Purchase #3	$233.94	7.442%	$251.3498	$251.35	$251.35	$251.30
Purchase #4	$107.29	4.532%	$112.1524	$112.15	$112.15	$112.20
Purchase #5	$49.61	13.632%	$56.3728	$56.37	$56.35	$56.40
Purchase #6	$164.96	9.347%	$180.3788	$180.38	$180.40	$180.40
Purchase #7	$204.92	6.345%	$217.9222	$217.92	$217.90	$217.90
7 purchase totals =	$1,033.78		$1,105.3463	$1,105.34	$1,105.30	$1,105.40