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	$225.88	3.333%	$233.4086	$233.41	$233.40	$233.40
Purchase #2	$106.89	4.558%	$111.762	$111.76	$111.75	$111.80
Purchase #3	$73.82	13.410%	$83.7193	$83.72	$83.70	$83.70
Purchase #4	$180.98	5.764%	$191.4117	$191.41	$191.40	$191.40
Purchase #5	$52.69	4.166%	$54.8851	$54.89	$54.90	$54.90
Purchase #6	$7.36	9.868%	$8.0863	$8.09	$8.10	$8.10
Purchase #7	$151.92	7.788%	$163.7515	$163.75	$163.75	$163.80
7 purchase totals =	$799.54		$847.0245	$847.03	$847.00	$847.10