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	$226.32	13.440%	$256.7374	$256.74	$256.75	$256.70
Purchase #2	$192.45	8.850%	$209.4818	$209.48	$209.50	$209.50
Purchase #3	$152.72	3.522%	$158.0988	$158.10	$158.10	$158.10
Purchase #4	$234.45	4.248%	$244.4094	$244.41	$244.40	$244.40
Purchase #5	$167.95	10.665%	$185.8619	$185.86	$185.85	$185.90
Purchase #6	$172.25	8.647%	$187.1445	$187.14	$187.15	$187.10
Purchase #7	$104.85	4.431%	$109.4959	$109.50	$109.50	$109.50
7 purchase totals =	$1,250.99		$1,351.2297	$1,351.23	$1,351.25	$1,351.20