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	$168.49	6.650%	$179.6946	$179.69	$179.70	$179.70
Purchase #2	$114.60	3.181%	$118.2454	$118.25	$118.25	$118.20
Purchase #3	$80.36	11.851%	$89.8835	$89.88	$89.90	$89.90
Purchase #4	$82.76	12.339%	$92.9718	$92.97	$92.95	$93.00
Purchase #5	$235.33	9.324%	$257.2722	$257.27	$257.25	$257.30
Purchase #6	$226.32	8.616%	$245.8197	$245.82	$245.80	$245.80
Purchase #7	$141.51	6.427%	$150.6048	$150.60	$150.60	$150.60
7 purchase totals =	$1,049.37		$1,134.4920	$1,134.48	$1,134.45	$1,134.50