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	$149.61	5.510%	$157.8535	$157.85	$157.85	$157.90
Purchase #2	$76.51	11.564%	$85.3576	$85.36	$85.35	$85.40
Purchase #3	$83.62	11.517%	$93.2505	$93.25	$93.25	$93.30
Purchase #4	$105.54	4.660%	$110.4582	$110.46	$110.45	$110.50
Purchase #5	$86.80	10.789%	$96.1649	$96.16	$96.15	$96.20
Purchase #6	$155.77	5.528%	$164.381	$164.38	$164.40	$164.40
Purchase #7	$39.30	9.188%	$42.9109	$42.91	$42.90	$42.90
7 purchase totals =	$697.15		$750.3766	$750.37	$750.35	$750.60