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	$233.73	6.552%	$249.044	$249.04	$249.05	$249.00
Purchase #2	$48.82	6.231%	$51.862	$51.86	$51.85	$51.90
Purchase #3	$50.85	11.109%	$56.4989	$56.50	$56.50	$56.50
Purchase #4	$126.45	10.761%	$140.0573	$140.06	$140.05	$140.10
Purchase #5	$63.58	11.642%	$70.982	$70.98	$71.00	$71.00
Purchase #6	$140.32	6.802%	$149.8646	$149.86	$149.85	$149.90
Purchase #7	$38.38	6.269%	$40.786	$40.79	$40.80	$40.80
7 purchase totals =	$702.13		$759.0948	$759.09	$759.10	$759.20