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	$211.40	9.195%	$230.8382	$230.84	$230.85	$230.80
Purchase #2	$52.60	5.592%	$55.5414	$55.54	$55.55	$55.50
Purchase #3	$53.71	13.184%	$60.7911	$60.79	$60.80	$60.80
Purchase #4	$167.87	11.444%	$187.081	$187.08	$187.10	$187.10
Purchase #5	$121.33	9.301%	$132.6149	$132.61	$132.60	$132.60
Purchase #6	$78.74	4.633%	$82.388	$82.39	$82.40	$82.40
Purchase #7	$163.33	9.515%	$178.8708	$178.87	$178.85	$178.90
7 purchase totals =	$848.98		$928.1254	$928.12	$928.15	$928.10