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	$161.28	6.558%	$171.8567	$171.86	$171.85	$171.90
Purchase #2	$32.39	13.722%	$36.8346	$36.83	$36.85	$36.80
Purchase #3	$149.96	12.388%	$168.537	$168.54	$168.55	$168.50
Purchase #4	$91.36	11.405%	$101.7796	$101.78	$101.80	$101.80
Purchase #5	$82.52	9.779%	$90.5896	$90.59	$90.60	$90.60
Purchase #6	$238.34	9.701%	$261.4614	$261.46	$261.45	$261.50
Purchase #7	$115.61	5.404%	$121.8576	$121.86	$121.85	$121.90
7 purchase totals =	$871.46		$952.9165	$952.92	$952.95	$953.00