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	$101.28	11.401%	$112.8269	$112.83	$112.85	$112.80
Purchase #2	$51.92	5.699%	$54.8789	$54.88	$54.90	$54.90
Purchase #3	$24.65	6.393%	$26.2259	$26.23	$26.25	$26.20
Purchase #4	$81.94	11.626%	$91.4663	$91.47	$91.45	$91.50
Purchase #5	$74.64	11.789%	$83.4393	$83.44	$83.45	$83.40
Purchase #6	$233.46	13.353%	$264.6339	$264.63	$264.65	$264.60
Purchase #7	$104.49	11.325%	$116.3235	$116.32	$116.30	$116.30
7 purchase totals =	$672.38		$749.7947	$749.80	$749.85	$749.70