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	$172.25	11.568%	$192.1759	$192.18	$192.20	$192.20
Purchase #2	$78.65	6.218%	$83.5405	$83.54	$83.55	$83.50
Purchase #3	$30.37	10.666%	$33.6093	$33.61	$33.60	$33.60
Purchase #4	$141.52	8.171%	$153.0836	$153.08	$153.10	$153.10
Purchase #5	$208.63	8.129%	$225.5895	$225.59	$225.60	$225.60
Purchase #6	$249.72	9.658%	$273.838	$273.84	$273.85	$273.80
Purchase #7	$152.64	8.372%	$165.419	$165.42	$165.40	$165.40
7 purchase totals =	$1,033.78		$1,127.2558	$1,127.26	$1,127.30	$1,127.20