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	$55.93	7.700%	$60.2366	$60.24	$60.25	$60.20
Purchase #2	$18.52	12.828%	$20.8957	$20.90	$20.90	$20.90
Purchase #3	$206.46	11.180%	$229.5422	$229.54	$229.55	$229.50
Purchase #4	$189.93	5.702%	$200.7598	$200.76	$200.75	$200.80
Purchase #5	$152.51	10.522%	$168.5571	$168.56	$168.55	$168.60
Purchase #6	$144.93	5.690%	$153.1765	$153.18	$153.20	$153.20
Purchase #7	$191.55	13.764%	$217.9149	$217.91	$217.90	$217.90
7 purchase totals =	$959.83		$1,051.0828	$1,051.09	$1,051.10	$1,051.10