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	$203.47	8.455%	$220.6734	$220.67	$220.65	$220.70
Purchase #2	$130.73	3.160%	$134.8611	$134.86	$134.85	$134.90
Purchase #3	$137.83	9.715%	$151.2202	$151.22	$151.20	$151.20
Purchase #4	$220.70	11.300%	$245.6391	$245.64	$245.65	$245.60
Purchase #5	$104.94	4.687%	$109.8585	$109.86	$109.85	$109.90
Purchase #6	$146.61	6.738%	$156.4886	$156.49	$156.50	$156.50
Purchase #7	$24.25	11.424%	$27.0203	$27.02	$27.00	$27.00
7 purchase totals =	$968.53		$1,045.7612	$1,045.76	$1,045.70	$1,045.80