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	$111.73	13.707%	$127.0448	$127.04	$127.05	$127.00
Purchase #2	$220.89	8.857%	$240.4542	$240.45	$240.45	$240.50
Purchase #3	$70.59	8.700%	$76.7313	$76.73	$76.75	$76.70
Purchase #4	$139.28	8.674%	$151.3611	$151.36	$151.35	$151.40
Purchase #5	$91.89	8.399%	$99.6078	$99.61	$99.60	$99.60
Purchase #6	$98.57	9.649%	$108.081	$108.08	$108.10	$108.10
Purchase #7	$196.60	9.652%	$215.5758	$215.58	$215.60	$215.60
7 purchase totals =	$929.55		$1,018.8560	$1,018.85	$1,018.90	$1,018.90