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	$96.45	10.155%	$106.2445	$106.24	$106.25	$106.20
Purchase #2	$113.92	4.379%	$118.9086	$118.91	$118.90	$118.90
Purchase #3	$45.82	12.821%	$51.6946	$51.69	$51.70	$51.70
Purchase #4	$238.92	9.235%	$260.9843	$260.98	$261.00	$261.00
Purchase #5	$216.99	10.673%	$240.1493	$240.15	$240.15	$240.10
Purchase #6	$100.44	10.852%	$111.3397	$111.34	$111.35	$111.30
Purchase #7	$236.74	12.843%	$267.1445	$267.14	$267.15	$267.10
7 purchase totals =	$1,049.28		$1,156.4655	$1,156.45	$1,156.50	$1,156.30