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	$175.60	7.139%	$188.1361	$188.14	$188.15	$188.10
Purchase #2	$80.45	6.653%	$85.8023	$85.80	$85.80	$85.80
Purchase #3	$30.54	10.874%	$33.8609	$33.86	$33.85	$33.90
Purchase #4	$17.52	4.831%	$18.3664	$18.37	$18.35	$18.40
Purchase #5	$245.72	5.677%	$259.6695	$259.67	$259.65	$259.70
Purchase #6	$208.57	12.834%	$235.3379	$235.34	$235.35	$235.30
Purchase #7	$218.56	3.554%	$226.3276	$226.33	$226.35	$226.30
7 purchase totals =	$976.96		$1,047.5007	$1,047.51	$1,047.50	$1,047.50