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	$51.64	4.312%	$53.8667	$53.87	$53.85	$53.90
Purchase #2	$63.84	9.862%	$70.1359	$70.14	$70.15	$70.10
Purchase #3	$43.76	4.808%	$45.864	$45.86	$45.85	$45.90
Purchase #4	$152.72	12.719%	$172.1445	$172.14	$172.15	$172.10
Purchase #5	$94.75	11.741%	$105.8746	$105.87	$105.85	$105.90
Purchase #6	$236.90	6.752%	$252.8955	$252.90	$252.90	$252.90
Purchase #7	$180.77	5.782%	$191.2221	$191.22	$191.20	$191.20
7 purchase totals =	$824.38		$892.0033	$892.00	$891.95	$892.00