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	$119.64	6.175%	$127.0278	$127.03	$127.05	$127.00
Purchase #2	$143.90	13.126%	$162.7883	$162.79	$162.80	$162.80
Purchase #3	$240.32	10.477%	$265.4983	$265.50	$265.50	$265.50
Purchase #4	$222.70	5.637%	$235.2536	$235.25	$235.25	$235.30
Purchase #5	$50.43	7.115%	$54.0181	$54.02	$54.00	$54.00
Purchase #6	$165.96	5.714%	$175.443	$175.44	$175.45	$175.40
Purchase #7	$69.62	13.865%	$79.2728	$79.27	$79.25	$79.30
7 purchase totals =	$1,012.57		$1,099.3019	$1,099.30	$1,099.30	$1,099.30