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	$209.28	9.852%	$229.8983	$229.90	$229.90	$229.90
Purchase #2	$127.39	12.438%	$143.2348	$143.23	$143.25	$143.20
Purchase #3	$80.37	11.325%	$89.4719	$89.47	$89.45	$89.50
Purchase #4	$242.55	11.199%	$269.7132	$269.71	$269.70	$269.70
Purchase #5	$22.71	11.378%	$25.2939	$25.29	$25.30	$25.30
Purchase #6	$198.96	6.329%	$211.5522	$211.55	$211.55	$211.60
Purchase #7	$96.57	12.296%	$108.4442	$108.44	$108.45	$108.40
7 purchase totals =	$977.83		$1,077.6085	$1,077.59	$1,077.60	$1,077.60