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	$48.27	12.844%	$54.4698	$54.47	$54.45	$54.50
Purchase #2	$199.31	12.164%	$223.5541	$223.55	$223.55	$223.60
Purchase #3	$9.25	11.826%	$10.3439	$10.34	$10.35	$10.30
Purchase #4	$147.43	10.375%	$162.7259	$162.73	$162.75	$162.70
Purchase #5	$169.62	11.104%	$188.4546	$188.45	$188.45	$188.50
Purchase #6	$98.75	4.675%	$103.3666	$103.37	$103.35	$103.40
Purchase #7	$173.51	10.641%	$191.9732	$191.97	$191.95	$192.00
7 purchase totals =	$846.14		$934.8881	$934.88	$934.85	$935.00