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	$229.53	10.235%	$253.0224	$253.02	$253.00	$253.00
Purchase #2	$123.37	7.410%	$132.5117	$132.51	$132.50	$132.50
Purchase #3	$39.74	10.297%	$43.832	$43.83	$43.85	$43.80
Purchase #4	$6.89	5.677%	$7.2811	$7.28	$7.30	$7.30
Purchase #5	$154.58	10.870%	$171.3828	$171.38	$171.40	$171.40
Purchase #6	$96.92	6.785%	$103.496	$103.50	$103.50	$103.50
Purchase #7	$230.91	13.676%	$262.4893	$262.49	$262.50	$262.50
7 purchase totals =	$881.94		$974.0153	$974.01	$974.05	$974.00