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	$125.55	4.831%	$131.6153	$131.62	$131.60	$131.60
Purchase #2	$108.37	11.531%	$120.8661	$120.87	$120.85	$120.90
Purchase #3	$173.45	3.648%	$179.7775	$179.78	$179.80	$179.80
Purchase #4	$232.77	9.616%	$255.1532	$255.15	$255.15	$255.20
Purchase #5	$50.56	6.736%	$53.9657	$53.97	$53.95	$54.00
Purchase #6	$150.69	11.484%	$167.9952	$168.00	$168.00	$168.00
Purchase #7	$231.32	11.803%	$258.6227	$258.62	$258.60	$258.60
7 purchase totals =	$1,072.71		$1,167.9957	$1,168.01	$1,167.95	$1,168.10