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	$87.35	12.365%	$98.1508	$98.15	$98.15	$98.20
Purchase #2	$159.32	6.111%	$169.056	$169.06	$169.05	$169.10
Purchase #3	$65.27	5.808%	$69.0609	$69.06	$69.05	$69.10
Purchase #4	$161.43	3.629%	$167.2883	$167.29	$167.30	$167.30
Purchase #5	$143.85	12.728%	$162.1592	$162.16	$162.15	$162.20
Purchase #6	$33.33	5.108%	$35.0325	$35.03	$35.05	$35.00
Purchase #7	$120.89	5.494%	$127.5317	$127.53	$127.55	$127.50
7 purchase totals =	$771.44		$828.2794	$828.28	$828.30	$828.40