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	$37.78	3.139%	$38.9659	$38.97	$38.95	$39.00
Purchase #2	$187.39	13.679%	$213.0231	$213.02	$213.00	$213.00
Purchase #3	$240.62	4.123%	$250.5408	$250.54	$250.55	$250.50
Purchase #4	$234.50	12.224%	$263.1653	$263.17	$263.15	$263.20
Purchase #5	$61.99	9.339%	$67.7792	$67.78	$67.80	$67.80
Purchase #6	$92.50	8.743%	$100.5873	$100.59	$100.60	$100.60
Purchase #7	$98.82	4.311%	$103.0801	$103.08	$103.10	$103.10
7 purchase totals =	$953.60		$1,037.1417	$1,037.15	$1,037.15	$1,037.20