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	$62.91	13.849%	$71.6224	$71.62	$71.60	$71.60
Purchase #2	$72.78	6.131%	$77.2421	$77.24	$77.25	$77.20
Purchase #3	$105.40	5.564%	$111.2645	$111.26	$111.25	$111.30
Purchase #4	$85.78	12.329%	$96.3558	$96.36	$96.35	$96.40
Purchase #5	$162.43	4.199%	$169.2504	$169.25	$169.25	$169.30
Purchase #6	$113.27	12.695%	$127.6496	$127.65	$127.65	$127.60
Purchase #7	$191.57	13.340%	$217.1254	$217.13	$217.15	$217.10
7 purchase totals =	$794.14		$870.5102	$870.51	$870.50	$870.50