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	$236.27	6.152%	$250.8053	$250.81	$250.80	$250.80
Purchase #2	$10.46	8.652%	$11.365	$11.37	$11.35	$11.40
Purchase #3	$83.86	8.686%	$91.1441	$91.14	$91.15	$91.10
Purchase #4	$81.50	4.274%	$84.9833	$84.98	$85.00	$85.00
Purchase #5	$169.96	13.136%	$192.2859	$192.29	$192.30	$192.30
Purchase #6	$198.63	6.277%	$211.098	$211.10	$211.10	$211.10
Purchase #7	$238.85	8.522%	$259.2048	$259.20	$259.20	$259.20
7 purchase totals =	$1,019.53		$1,100.8864	$1,100.89	$1,100.90	$1,100.90