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	$153.82	11.263%	$171.1447	$171.14	$171.15	$171.10
Purchase #2	$52.92	13.279%	$59.9472	$59.95	$59.95	$59.90
Purchase #3	$223.61	5.365%	$235.6067	$235.61	$235.60	$235.60
Purchase #4	$111.98	6.182%	$118.9026	$118.90	$118.90	$118.90
Purchase #5	$168.43	3.412%	$174.1768	$174.18	$174.20	$174.20
Purchase #6	$242.84	4.598%	$254.0058	$254.01	$254.00	$254.00
Purchase #7	$15.28	13.734%	$17.3786	$17.38	$17.40	$17.40
7 purchase totals =	$968.88		$1,031.1624	$1,031.17	$1,031.20	$1,031.10