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	$37.94	9.682%	$41.6134	$41.61	$41.60	$41.60
Purchase #2	$197.33	7.679%	$212.483	$212.48	$212.50	$212.50
Purchase #3	$158.29	6.169%	$168.0549	$168.05	$168.05	$168.10
Purchase #4	$144.67	13.704%	$164.4956	$164.50	$164.50	$164.50
Purchase #5	$239.36	9.206%	$261.3955	$261.40	$261.40	$261.40
Purchase #6	$37.77	4.858%	$39.6049	$39.60	$39.60	$39.60
Purchase #7	$250.38	7.606%	$269.4239	$269.42	$269.40	$269.40
7 purchase totals =	$1,065.74		$1,157.0712	$1,157.06	$1,157.05	$1,157.10