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	$87.30	10.345%	$96.3312	$96.33	$96.35	$96.30
Purchase #2	$61.84	8.791%	$67.2764	$67.28	$67.30	$67.30
Purchase #3	$42.52	12.867%	$47.991	$47.99	$48.00	$48.00
Purchase #4	$168.39	5.810%	$178.1735	$178.17	$178.15	$178.20
Purchase #5	$49.64	5.688%	$52.4635	$52.46	$52.45	$52.50
Purchase #6	$29.33	7.798%	$31.6172	$31.62	$31.60	$31.60
Purchase #7	$98.41	4.271%	$102.6131	$102.61	$102.60	$102.60
7 purchase totals =	$537.43		$576.4659	$576.46	$576.45	$576.50