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	$31.25	4.871%	$32.7722	$32.77	$32.75	$32.80
Purchase #2	$188.73	11.550%	$210.5283	$210.53	$210.55	$210.50
Purchase #3	$106.38	5.605%	$112.3426	$112.34	$112.35	$112.30
Purchase #4	$143.63	13.332%	$162.7788	$162.78	$162.80	$162.80
Purchase #5	$151.59	4.326%	$158.1478	$158.15	$158.15	$158.10
Purchase #6	$220.68	13.307%	$250.0459	$250.05	$250.05	$250.00
Purchase #7	$196.50	5.202%	$206.7219	$206.72	$206.70	$206.70
7 purchase totals =	$1,038.76		$1,133.3375	$1,133.34	$1,133.35	$1,133.20