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	$73.87	5.566%	$77.9816	$77.98	$78.00	$78.00
Purchase #2	$52.81	4.685%	$55.2841	$55.28	$55.30	$55.30
Purchase #3	$250.28	6.249%	$265.92	$265.92	$265.90	$265.90
Purchase #4	$32.68	13.871%	$37.213	$37.21	$37.20	$37.20
Purchase #5	$116.81	6.247%	$124.1071	$124.11	$124.10	$124.10
Purchase #6	$145.86	5.273%	$153.5512	$153.55	$153.55	$153.60
Purchase #7	$179.45	11.695%	$200.4367	$200.44	$200.45	$200.40
7 purchase totals =	$851.76		$914.4937	$914.49	$914.50	$914.50