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	$169.53	5.280%	$178.4812	$178.48	$178.50	$178.50
Purchase #2	$89.32	11.404%	$99.5061	$99.51	$99.50	$99.50
Purchase #3	$116.82	9.518%	$127.9389	$127.94	$127.95	$127.90
Purchase #4	$197.81	6.368%	$210.4065	$210.41	$210.40	$210.40
Purchase #5	$131.68	8.528%	$142.9097	$142.91	$142.90	$142.90
Purchase #6	$76.94	5.339%	$81.0478	$81.05	$81.05	$81.00
Purchase #7	$88.93	7.717%	$95.7927	$95.79	$95.80	$95.80
7 purchase totals =	$871.03		$936.0829	$936.09	$936.10	$936.00