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	$88.42	9.245%	$96.5944	$96.59	$96.60	$96.60
Purchase #2	$6.52	11.782%	$7.2882	$7.29	$7.30	$7.30
Purchase #3	$194.99	10.522%	$215.5068	$215.51	$215.50	$215.50
Purchase #4	$18.29	10.853%	$20.275	$20.28	$20.30	$20.30
Purchase #5	$208.56	4.743%	$218.452	$218.45	$218.45	$218.50
Purchase #6	$178.64	6.844%	$190.8661	$190.87	$190.85	$190.90
Purchase #7	$219.51	11.456%	$244.6571	$244.66	$244.65	$244.70
7 purchase totals =	$914.93		$993.6396	$993.65	$993.65	$993.80