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	$96.33	13.760%	$109.585	$109.59	$109.60	$109.60
Purchase #2	$114.26	5.258%	$120.2678	$120.27	$120.25	$120.30
Purchase #3	$71.55	7.442%	$76.8748	$76.87	$76.85	$76.90
Purchase #4	$81.67	9.671%	$89.5683	$89.57	$89.55	$89.60
Purchase #5	$104.71	3.177%	$108.0366	$108.04	$108.05	$108.00
Purchase #6	$75.65	6.526%	$80.5869	$80.59	$80.60	$80.60
Purchase #7	$202.26	4.678%	$211.7217	$211.72	$211.70	$211.70
7 purchase totals =	$746.43		$796.6411	$796.65	$796.60	$796.70