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	$88.57	11.323%	$98.5988	$98.60	$98.60	$98.60
Purchase #2	$162.57	5.499%	$171.5097	$171.51	$171.50	$171.50
Purchase #3	$122.65	5.676%	$129.6116	$129.61	$129.60	$129.60
Purchase #4	$101.52	4.320%	$105.9057	$105.91	$105.90	$105.90
Purchase #5	$199.52	5.664%	$210.8208	$210.82	$210.80	$210.80
Purchase #6	$16.80	3.391%	$17.3697	$17.37	$17.35	$17.40
Purchase #7	$112.53	13.418%	$127.6293	$127.63	$127.65	$127.60
7 purchase totals =	$804.16		$861.4456	$861.45	$861.40	$861.40