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	$31.85	13.495%	$36.1482	$36.15	$36.15	$36.10
Purchase #2	$33.37	11.811%	$37.3113	$37.31	$37.30	$37.30
Purchase #3	$11.81	13.704%	$13.4284	$13.43	$13.45	$13.40
Purchase #4	$91.30	8.682%	$99.2267	$99.23	$99.25	$99.20
Purchase #5	$62.91	5.572%	$66.4153	$66.42	$66.40	$66.40
Purchase #6	$96.88	9.296%	$105.886	$105.89	$105.90	$105.90
Purchase #7	$86.72	11.266%	$96.4899	$96.49	$96.50	$96.50
7 purchase totals =	$414.84		$454.9058	$454.92	$454.95	$454.80