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	$12.26	6.564%	$13.0647	$13.06	$13.05	$13.10
Purchase #2	$39.81	10.474%	$43.9797	$43.98	$44.00	$44.00
Purchase #3	$155.46	10.754%	$172.1782	$172.18	$172.20	$172.20
Purchase #4	$202.87	4.420%	$211.8369	$211.84	$211.85	$211.80
Purchase #5	$81.89	9.181%	$89.4083	$89.41	$89.40	$89.40
Purchase #6	$127.54	11.406%	$142.0872	$142.09	$142.10	$142.10
Purchase #7	$109.48	13.264%	$124.0014	$124.00	$124.00	$124.00
7 purchase totals =	$729.31		$796.5564	$796.56	$796.60	$796.60