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	$233.80	12.731%	$263.5651	$263.57	$263.55	$263.60
Purchase #2	$178.27	8.222%	$192.9274	$192.93	$192.95	$192.90
Purchase #3	$53.45	3.665%	$55.4089	$55.41	$55.40	$55.40
Purchase #4	$199.36	4.110%	$207.5537	$207.55	$207.55	$207.60
Purchase #5	$67.64	5.161%	$71.1309	$71.13	$71.15	$71.10
Purchase #6	$52.36	13.681%	$59.5234	$59.52	$59.50	$59.50
Purchase #7	$91.46	5.622%	$96.6019	$96.60	$96.60	$96.60
7 purchase totals =	$876.34		$946.7113	$946.71	$946.70	$946.70