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	$142.76	4.759%	$149.5539	$149.55	$149.55	$149.60
Purchase #2	$186.69	13.499%	$211.8913	$211.89	$211.90	$211.90
Purchase #3	$213.26	4.527%	$222.9143	$222.91	$222.90	$222.90
Purchase #4	$209.32	10.757%	$231.8366	$231.84	$231.85	$231.80
Purchase #5	$79.28	12.199%	$88.9514	$88.95	$88.95	$89.00
Purchase #6	$55.76	12.440%	$62.6965	$62.70	$62.70	$62.70
Purchase #7	$111.59	5.288%	$117.4909	$117.49	$117.50	$117.50
7 purchase totals =	$998.66		$1,085.3349	$1,085.33	$1,085.35	$1,085.40