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	$127.29	11.330%	$141.712	$141.71	$141.70	$141.70
Purchase #2	$46.50	3.324%	$48.0457	$48.05	$48.05	$48.00
Purchase #3	$245.58	5.651%	$259.4577	$259.46	$259.45	$259.50
Purchase #4	$191.60	7.746%	$206.4413	$206.44	$206.45	$206.40
Purchase #5	$28.32	4.722%	$29.6573	$29.66	$29.65	$29.70
Purchase #6	$164.35	10.401%	$181.444	$181.44	$181.45	$181.40
Purchase #7	$196.33	13.218%	$222.2809	$222.28	$222.30	$222.30
7 purchase totals =	$999.97		$1,089.0389	$1,089.04	$1,089.05	$1,089.00