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	$148.30	13.495%	$168.3131	$168.31	$168.30	$168.30
Purchase #2	$17.98	5.222%	$18.9189	$18.92	$18.90	$18.90
Purchase #3	$217.77	11.655%	$243.1511	$243.15	$243.15	$243.20
Purchase #4	$70.55	12.683%	$79.4979	$79.50	$79.50	$79.50
Purchase #5	$153.26	12.433%	$172.3148	$172.31	$172.30	$172.30
Purchase #6	$94.45	8.542%	$102.5179	$102.52	$102.50	$102.50
Purchase #7	$14.55	5.392%	$15.3345	$15.33	$15.35	$15.30
7 purchase totals =	$716.86		$800.0482	$800.04	$800.00	$800.00