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	$118.71	11.312%	$132.1385	$132.14	$132.15	$132.10
Purchase #2	$189.90	5.591%	$200.5173	$200.52	$200.50	$200.50
Purchase #3	$196.91	11.480%	$219.5153	$219.52	$219.50	$219.50
Purchase #4	$109.65	8.747%	$119.2411	$119.24	$119.25	$119.20
Purchase #5	$59.99	9.723%	$65.8228	$65.82	$65.80	$65.80
Purchase #6	$198.66	3.113%	$204.8443	$204.84	$204.85	$204.80
Purchase #7	$16.73	12.498%	$18.8209	$18.82	$18.80	$18.80
7 purchase totals =	$890.55		$960.9002	$960.90	$960.85	$960.70