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	$142.81	6.535%	$152.1426	$152.14	$152.15	$152.10
Purchase #2	$9.79	5.655%	$10.3436	$10.34	$10.35	$10.30
Purchase #3	$208.99	9.288%	$228.401	$228.40	$228.40	$228.40
Purchase #4	$55.72	9.194%	$60.8429	$60.84	$60.85	$60.80
Purchase #5	$218.82	10.861%	$242.586	$242.59	$242.60	$242.60
Purchase #6	$86.67	4.824%	$90.851	$90.85	$90.85	$90.90
Purchase #7	$141.96	10.272%	$156.5421	$156.54	$156.55	$156.50
7 purchase totals =	$864.76		$941.7092	$941.70	$941.75	$941.60