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	$151.93	9.375%	$166.1734	$166.17	$166.15	$166.20
Purchase #2	$17.46	3.526%	$18.0756	$18.08	$18.10	$18.10
Purchase #3	$67.36	4.334%	$70.2794	$70.28	$70.30	$70.30
Purchase #4	$78.72	5.248%	$82.8512	$82.85	$82.85	$82.90
Purchase #5	$67.53	4.182%	$70.3541	$70.35	$70.35	$70.40
Purchase #6	$54.70	4.778%	$57.3136	$57.31	$57.30	$57.30
Purchase #7	$240.98	10.642%	$266.6251	$266.63	$266.65	$266.60
7 purchase totals =	$678.68		$731.6724	$731.67	$731.70	$731.80