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	$65.53	12.178%	$73.5102	$73.51	$73.50	$73.50
Purchase #2	$109.74	4.211%	$114.3612	$114.36	$114.35	$114.40
Purchase #3	$146.51	4.139%	$152.574	$152.57	$152.55	$152.60
Purchase #4	$248.65	4.366%	$259.5061	$259.51	$259.50	$259.50
Purchase #5	$199.85	13.462%	$226.7538	$226.75	$226.75	$226.80
Purchase #6	$82.51	6.768%	$88.0943	$88.09	$88.10	$88.10
Purchase #7	$148.27	12.194%	$166.35	$166.35	$166.35	$166.40
7 purchase totals =	$1,001.06		$1,081.1496	$1,081.14	$1,081.10	$1,081.30