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	$92.68	5.510%	$97.7867	$97.79	$97.80	$97.80
Purchase #2	$208.82	12.215%	$234.3274	$234.33	$234.35	$234.30
Purchase #3	$175.80	5.519%	$185.5024	$185.50	$185.50	$185.50
Purchase #4	$215.43	13.730%	$245.0085	$245.01	$245.00	$245.00
Purchase #5	$109.48	11.541%	$122.1151	$122.12	$122.10	$122.10
Purchase #6	$155.32	13.245%	$175.8921	$175.89	$175.90	$175.90
Purchase #7	$20.82	3.153%	$21.4765	$21.48	$21.50	$21.50
7 purchase totals =	$978.35		$1,082.1087	$1,082.12	$1,082.15	$1,082.10