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	$163.27	13.704%	$185.6445	$185.64	$185.65	$185.60
Purchase #2	$95.98	8.535%	$104.1719	$104.17	$104.15	$104.20
Purchase #3	$205.55	10.476%	$227.0834	$227.08	$227.10	$227.10
Purchase #4	$125.93	9.365%	$137.7233	$137.72	$137.70	$137.70
Purchase #5	$55.63	4.216%	$57.9754	$57.98	$58.00	$58.00
Purchase #6	$91.80	9.547%	$100.5641	$100.56	$100.55	$100.60
Purchase #7	$77.92	10.574%	$86.1593	$86.16	$86.15	$86.20
7 purchase totals =	$816.08		$899.3219	$899.31	$899.30	$899.40