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	$131.38	11.839%	$146.9341	$146.93	$146.95	$146.90
Purchase #2	$73.75	10.633%	$81.5918	$81.59	$81.60	$81.60
Purchase #3	$121.38	4.866%	$127.2864	$127.29	$127.30	$127.30
Purchase #4	$41.70	6.318%	$44.3346	$44.33	$44.35	$44.30
Purchase #5	$98.56	11.649%	$110.0413	$110.04	$110.05	$110.00
Purchase #6	$113.49	5.747%	$120.0123	$120.01	$120.00	$120.00
Purchase #7	$116.45	12.765%	$131.3148	$131.31	$131.30	$131.30
7 purchase totals =	$696.71		$761.5153	$761.50	$761.55	$761.40