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	$186.61	11.159%	$207.4338	$207.43	$207.45	$207.40
Purchase #2	$211.88	5.191%	$222.8787	$222.88	$222.90	$222.90
Purchase #3	$136.83	7.602%	$147.2318	$147.23	$147.25	$147.20
Purchase #4	$185.78	5.754%	$196.4698	$196.47	$196.45	$196.50
Purchase #5	$54.43	11.475%	$60.6758	$60.68	$60.70	$60.70
Purchase #6	$216.30	3.294%	$223.4249	$223.42	$223.40	$223.40
Purchase #7	$237.72	10.714%	$263.1893	$263.19	$263.20	$263.20
7 purchase totals =	$1,229.55		$1,321.3041	$1,321.30	$1,321.35	$1,321.30