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	$174.58	6.508%	$185.9417	$185.94	$185.95	$185.90
Purchase #2	$208.36	6.552%	$222.0117	$222.01	$222.00	$222.00
Purchase #3	$214.48	12.823%	$241.9828	$241.98	$242.00	$242.00
Purchase #4	$103.83	7.302%	$111.4117	$111.41	$111.40	$111.40
Purchase #5	$214.26	4.133%	$223.1154	$223.12	$223.10	$223.10
Purchase #6	$31.47	8.419%	$34.1195	$34.12	$34.10	$34.10
Purchase #7	$52.81	12.811%	$59.5755	$59.58	$59.60	$59.60
7 purchase totals =	$999.79		$1,078.1583	$1,078.16	$1,078.15	$1,078.10