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	$168.63	4.595%	$176.3785	$176.38	$176.40	$176.40
Purchase #2	$6.92	8.180%	$7.4861	$7.49	$7.50	$7.50
Purchase #3	$226.87	12.623%	$255.5078	$255.51	$255.50	$255.50
Purchase #4	$199.87	11.608%	$223.0709	$223.07	$223.05	$223.10
Purchase #5	$245.78	11.327%	$273.6195	$273.62	$273.60	$273.60
Purchase #6	$209.30	4.281%	$218.2601	$218.26	$218.25	$218.30
Purchase #7	$51.87	8.574%	$56.3173	$56.32	$56.30	$56.30
7 purchase totals =	$1,109.24		$1,210.6402	$1,210.65	$1,210.60	$1,210.70