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	$64.96	11.214%	$72.2446	$72.24	$72.25	$72.20
Purchase #2	$233.88	12.732%	$263.6576	$263.66	$263.65	$263.70
Purchase #3	$150.53	11.813%	$168.3121	$168.31	$168.30	$168.30
Purchase #4	$196.82	4.314%	$205.3108	$205.31	$205.30	$205.30
Purchase #5	$73.68	6.858%	$78.733	$78.73	$78.75	$78.70
Purchase #6	$47.45	9.179%	$51.8054	$51.81	$51.80	$51.80
Purchase #7	$115.97	8.213%	$125.4946	$125.49	$125.50	$125.50
7 purchase totals =	$883.29		$965.5581	$965.55	$965.55	$965.50