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	$60.33	3.691%	$62.5568	$62.56	$62.55	$62.60
Purchase #2	$41.92	9.303%	$45.8198	$45.82	$45.80	$45.80
Purchase #3	$140.62	6.666%	$149.9937	$149.99	$150.00	$150.00
Purchase #4	$81.78	4.149%	$85.1731	$85.17	$85.15	$85.20
Purchase #5	$52.31	4.425%	$54.6247	$54.62	$54.60	$54.60
Purchase #6	$67.56	7.598%	$72.6932	$72.69	$72.70	$72.70
Purchase #7	$208.98	3.653%	$216.614	$216.61	$216.60	$216.60
7 purchase totals =	$653.50		$687.4753	$687.46	$687.40	$687.50