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	$140.88	9.347%	$154.0481	$154.05	$154.05	$154.00
Purchase #2	$88.46	8.823%	$96.2648	$96.26	$96.25	$96.30
Purchase #3	$40.80	5.431%	$43.0158	$43.02	$43.00	$43.00
Purchase #4	$38.89	3.839%	$40.383	$40.38	$40.40	$40.40
Purchase #5	$234.48	6.554%	$249.8478	$249.85	$249.85	$249.80
Purchase #6	$85.57	12.721%	$96.4554	$96.46	$96.45	$96.50
Purchase #7	$105.59	3.400%	$109.1801	$109.18	$109.20	$109.20
7 purchase totals =	$734.67		$789.1950	$789.20	$789.20	$789.20