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	$31.47	12.513%	$35.4078	$35.41	$35.40	$35.40
Purchase #2	$204.25	9.201%	$223.043	$223.04	$223.05	$223.00
Purchase #3	$154.85	6.432%	$164.81	$164.81	$164.80	$164.80
Purchase #4	$161.33	4.152%	$168.0284	$168.03	$168.05	$168.00
Purchase #5	$110.72	12.823%	$124.9176	$124.92	$124.90	$124.90
Purchase #6	$169.55	6.131%	$179.9451	$179.95	$179.95	$179.90
Purchase #7	$243.32	3.124%	$250.9213	$250.92	$250.90	$250.90
7 purchase totals =	$1,075.49		$1,147.0732	$1,147.08	$1,147.05	$1,146.90