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	$104.98	6.191%	$111.4793	$111.48	$111.50	$111.50
Purchase #2	$242.41	4.188%	$252.5621	$252.56	$252.55	$252.60
Purchase #3	$118.52	7.667%	$127.6069	$127.61	$127.60	$127.60
Purchase #4	$148.80	9.204%	$162.4956	$162.50	$162.50	$162.50
Purchase #5	$167.53	11.200%	$186.2934	$186.29	$186.30	$186.30
Purchase #6	$79.66	9.689%	$87.3783	$87.38	$87.40	$87.40
Purchase #7	$62.49	11.871%	$69.9082	$69.91	$69.90	$69.90
7 purchase totals =	$924.39		$997.7238	$997.73	$997.75	$997.80