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	$179.34	9.372%	$196.1477	$196.15	$196.15	$196.10
Purchase #2	$242.34	3.783%	$251.5077	$251.51	$251.50	$251.50
Purchase #3	$129.65	5.321%	$136.5487	$136.55	$136.55	$136.50
Purchase #4	$244.89	12.431%	$275.3323	$275.33	$275.35	$275.30
Purchase #5	$100.28	3.740%	$104.0305	$104.03	$104.05	$104.00
Purchase #6	$29.82	12.474%	$33.5397	$33.54	$33.55	$33.50
Purchase #7	$56.59	13.679%	$64.3309	$64.33	$64.35	$64.30
7 purchase totals =	$982.91		$1,061.4375	$1,061.44	$1,061.50	$1,061.20