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	$43.39	3.460%	$44.8913	$44.89	$44.90	$44.90
Purchase #2	$65.35	9.306%	$71.4315	$71.43	$71.45	$71.40
Purchase #3	$162.74	3.659%	$168.6947	$168.69	$168.70	$168.70
Purchase #4	$213.99	5.175%	$225.064	$225.06	$225.05	$225.10
Purchase #5	$35.79	4.114%	$37.2624	$37.26	$37.25	$37.30
Purchase #6	$172.85	6.841%	$184.6747	$184.67	$184.65	$184.70
Purchase #7	$63.28	11.824%	$70.7622	$70.76	$70.75	$70.80
7 purchase totals =	$757.39		$802.7808	$802.76	$802.75	$802.90