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	$114.35	11.624%	$127.642	$127.64	$127.65	$127.60
Purchase #2	$100.81	3.531%	$104.3696	$104.37	$104.35	$104.40
Purchase #3	$32.34	9.858%	$35.5281	$35.53	$35.55	$35.50
Purchase #4	$107.98	3.346%	$111.593	$111.59	$111.60	$111.60
Purchase #5	$143.38	3.294%	$148.1029	$148.10	$148.10	$148.10
Purchase #6	$115.58	11.874%	$129.304	$129.30	$129.30	$129.30
Purchase #7	$69.73	9.753%	$76.5308	$76.53	$76.55	$76.50
7 purchase totals =	$684.17		$733.0704	$733.06	$733.10	$733.00