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	$163.96	13.396%	$185.9241	$185.92	$185.90	$185.90
Purchase #2	$45.63	6.499%	$48.5955	$48.60	$48.60	$48.60
Purchase #3	$200.58	7.847%	$216.3195	$216.32	$216.30	$216.30
Purchase #4	$107.36	10.185%	$118.2946	$118.29	$118.30	$118.30
Purchase #5	$159.72	9.486%	$174.871	$174.87	$174.85	$174.90
Purchase #6	$40.25	5.272%	$42.372	$42.37	$42.35	$42.40
Purchase #7	$216.83	12.180%	$243.2399	$243.24	$243.25	$243.20
7 purchase totals =	$934.33		$1,029.6166	$1,029.61	$1,029.55	$1,029.60