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	$125.50	6.386%	$133.5144	$133.51	$133.50	$133.50
Purchase #2	$152.28	12.327%	$171.0516	$171.05	$171.05	$171.10
Purchase #3	$59.57	6.271%	$63.3056	$63.31	$63.30	$63.30
Purchase #4	$238.67	4.521%	$249.4603	$249.46	$249.45	$249.50
Purchase #5	$32.68	9.748%	$35.8656	$35.87	$35.85	$35.90
Purchase #6	$85.98	3.701%	$89.1621	$89.16	$89.15	$89.20
Purchase #7	$99.42	11.415%	$110.7688	$110.77	$110.75	$110.80
7 purchase totals =	$794.10		$853.1284	$853.13	$853.05	$853.30