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	$43.25	11.732%	$48.3241	$48.32	$48.30	$48.30
Purchase #2	$149.93	12.118%	$168.0985	$168.10	$168.10	$168.10
Purchase #3	$165.85	7.869%	$178.9007	$178.90	$178.90	$178.90
Purchase #4	$207.31	7.836%	$223.5548	$223.55	$223.55	$223.60
Purchase #5	$227.42	12.237%	$255.2494	$255.25	$255.25	$255.20
Purchase #6	$127.54	9.862%	$140.118	$140.12	$140.10	$140.10
Purchase #7	$185.85	11.228%	$206.7172	$206.72	$206.70	$206.70
7 purchase totals =	$1,107.15		$1,220.9627	$1,220.96	$1,220.90	$1,220.90