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	$70.76	8.346%	$76.6656	$76.67	$76.65	$76.70
Purchase #2	$35.52	9.488%	$38.8901	$38.89	$38.90	$38.90
Purchase #3	$219.89	6.369%	$233.8948	$233.89	$233.90	$233.90
Purchase #4	$80.50	3.827%	$83.5807	$83.58	$83.60	$83.60
Purchase #5	$86.86	10.737%	$96.1862	$96.19	$96.20	$96.20
Purchase #6	$166.98	4.457%	$174.4223	$174.42	$174.40	$174.40
Purchase #7	$140.45	7.548%	$151.0512	$151.05	$151.05	$151.10
7 purchase totals =	$800.96		$854.6909	$854.69	$854.70	$854.80