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	$164.26	4.225%	$171.2	$171.20	$171.20	$171.20
Purchase #2	$54.77	4.275%	$57.1114	$57.11	$57.10	$57.10
Purchase #3	$54.92	11.407%	$61.1847	$61.18	$61.20	$61.20
Purchase #4	$160.39	13.492%	$182.0298	$182.03	$182.05	$182.00
Purchase #5	$201.93	6.615%	$215.2877	$215.29	$215.30	$215.30
Purchase #6	$152.33	7.710%	$164.0746	$164.07	$164.05	$164.10
Purchase #7	$114.40	11.462%	$127.5125	$127.51	$127.50	$127.50
7 purchase totals =	$903.00		$978.4007	$978.39	$978.40	$978.40