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	$93.46	10.280%	$103.0677	$103.07	$103.05	$103.10
Purchase #2	$47.59	3.398%	$49.2071	$49.21	$49.20	$49.20
Purchase #3	$109.89	12.821%	$123.979	$123.98	$124.00	$124.00
Purchase #4	$200.64	9.312%	$219.3236	$219.32	$219.30	$219.30
Purchase #5	$213.42	11.185%	$237.291	$237.29	$237.30	$237.30
Purchase #6	$238.45	6.821%	$254.7147	$254.71	$254.70	$254.70
Purchase #7	$28.82	11.268%	$32.0674	$32.07	$32.05	$32.10
7 purchase totals =	$932.27		$1,019.6505	$1,019.65	$1,019.60	$1,019.70