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	$173.43	10.773%	$192.1136	$192.11	$192.10	$192.10
Purchase #2	$96.35	3.206%	$99.439	$99.44	$99.45	$99.40
Purchase #3	$47.91	8.566%	$52.014	$52.01	$52.00	$52.00
Purchase #4	$53.47	11.183%	$59.4496	$59.45	$59.45	$59.40
Purchase #5	$132.29	4.327%	$138.0142	$138.01	$138.00	$138.00
Purchase #6	$177.65	7.653%	$191.2456	$191.25	$191.25	$191.20
Purchase #7	$241.78	11.838%	$270.4019	$270.40	$270.40	$270.40
7 purchase totals =	$922.88		$1,002.6779	$1,002.67	$1,002.65	$1,002.50