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	$86.26	5.423%	$90.9379	$90.94	$90.95	$90.90
Purchase #2	$88.28	7.489%	$94.8913	$94.89	$94.90	$94.90
Purchase #3	$68.77	9.661%	$75.4139	$75.41	$75.40	$75.40
Purchase #4	$87.88	9.665%	$96.3736	$96.37	$96.35	$96.40
Purchase #5	$104.34	3.863%	$108.3707	$108.37	$108.35	$108.40
Purchase #6	$229.54	11.609%	$256.1873	$256.19	$256.20	$256.20
Purchase #7	$56.32	5.186%	$59.2408	$59.24	$59.25	$59.20
7 purchase totals =	$721.39		$781.4155	$781.41	$781.40	$781.40