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	$63.52	13.483%	$72.0844	$72.08	$72.10	$72.10
Purchase #2	$110.78	7.709%	$119.32	$119.32	$119.30	$119.30
Purchase #3	$14.59	11.843%	$16.3179	$16.32	$16.30	$16.30
Purchase #4	$59.43	3.375%	$61.4358	$61.44	$61.45	$61.40
Purchase #5	$185.95	13.420%	$210.9045	$210.90	$210.90	$210.90
Purchase #6	$36.44	10.175%	$40.1478	$40.15	$40.15	$40.10
Purchase #7	$48.28	10.301%	$53.2533	$53.25	$53.25	$53.30
7 purchase totals =	$518.99		$573.4637	$573.46	$573.45	$573.40