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	$213.78	8.139%	$231.1796	$231.18	$231.20	$231.20
Purchase #2	$52.32	3.333%	$54.0638	$54.06	$54.05	$54.10
Purchase #3	$82.42	4.143%	$85.8347	$85.83	$85.85	$85.80
Purchase #4	$222.88	11.337%	$248.1479	$248.15	$248.15	$248.10
Purchase #5	$24.49	12.516%	$27.5552	$27.56	$27.55	$27.60
Purchase #6	$172.40	7.588%	$185.4817	$185.48	$185.50	$185.50
Purchase #7	$210.96	4.739%	$220.9574	$220.96	$220.95	$221.00
7 purchase totals =	$979.25		$1,053.2203	$1,053.22	$1,053.25	$1,053.30