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	$248.41	8.307%	$269.0454	$269.05	$269.05	$269.00
Purchase #2	$125.65	12.179%	$140.9529	$140.95	$140.95	$141.00
Purchase #3	$65.34	8.821%	$71.1036	$71.10	$71.10	$71.10
Purchase #4	$152.54	9.858%	$167.5774	$167.58	$167.60	$167.60
Purchase #5	$120.77	8.789%	$131.3845	$131.38	$131.40	$131.40
Purchase #6	$151.95	6.802%	$162.2856	$162.29	$162.30	$162.30
Purchase #7	$138.38	8.425%	$150.0385	$150.04	$150.05	$150.00
7 purchase totals =	$1,003.04		$1,092.3879	$1,092.39	$1,092.45	$1,092.40