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	$153.71	11.435%	$171.2867	$171.29	$171.30	$171.30
Purchase #2	$218.29	9.163%	$238.2919	$238.29	$238.30	$238.30
Purchase #3	$222.34	4.859%	$233.1435	$233.14	$233.15	$233.10
Purchase #4	$95.68	13.185%	$108.2954	$108.30	$108.30	$108.30
Purchase #5	$39.69	10.658%	$43.9202	$43.92	$43.90	$43.90
Purchase #6	$152.32	9.175%	$166.2954	$166.30	$166.30	$166.30
Purchase #7	$208.25	13.455%	$236.27	$236.27	$236.25	$236.30
7 purchase totals =	$1,090.28		$1,197.5031	$1,197.51	$1,197.50	$1,197.50