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	$103.98	4.656%	$108.8213	$108.82	$108.80	$108.80
Purchase #2	$169.90	9.184%	$185.5036	$185.50	$185.50	$185.50
Purchase #3	$139.92	6.232%	$148.6398	$148.64	$148.65	$148.60
Purchase #4	$82.62	12.675%	$93.0921	$93.09	$93.10	$93.10
Purchase #5	$98.69	12.228%	$110.7578	$110.76	$110.75	$110.80
Purchase #6	$176.53	6.577%	$188.1404	$188.14	$188.15	$188.10
Purchase #7	$216.37	4.853%	$226.8704	$226.87	$226.85	$226.90
7 purchase totals =	$988.01		$1,061.8254	$1,061.82	$1,061.80	$1,061.80