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	$72.81	6.727%	$77.7079	$77.71	$77.70	$77.70
Purchase #2	$87.69	9.449%	$95.9758	$95.98	$96.00	$96.00
Purchase #3	$35.49	9.589%	$38.8931	$38.89	$38.90	$38.90
Purchase #4	$30.49	9.422%	$33.3628	$33.36	$33.35	$33.40
Purchase #5	$56.45	5.661%	$59.6456	$59.65	$59.65	$59.60
Purchase #6	$83.67	8.565%	$90.8363	$90.84	$90.85	$90.80
Purchase #7	$39.38	9.314%	$43.0479	$43.05	$43.05	$43.00
7 purchase totals =	$405.98		$439.4694	$439.48	$439.50	$439.40