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	$86.81	11.206%	$96.5379	$96.54	$96.55	$96.50
Purchase #2	$46.63	4.300%	$48.6351	$48.64	$48.65	$48.60
Purchase #3	$44.98	10.788%	$49.8324	$49.83	$49.85	$49.80
Purchase #4	$185.29	10.566%	$204.8677	$204.87	$204.85	$204.90
Purchase #5	$8.59	3.490%	$8.8898	$8.89	$8.90	$8.90
Purchase #6	$198.89	10.278%	$219.3319	$219.33	$219.35	$219.30
Purchase #7	$145.70	5.325%	$153.4585	$153.46	$153.45	$153.50
7 purchase totals =	$716.89		$781.5533	$781.56	$781.60	$781.50