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	$235.28	13.421%	$266.8569	$266.86	$266.85	$266.90
Purchase #2	$29.89	8.134%	$32.3213	$32.32	$32.30	$32.30
Purchase #3	$94.58	11.630%	$105.5797	$105.58	$105.60	$105.60
Purchase #4	$165.40	11.453%	$184.3433	$184.34	$184.35	$184.30
Purchase #5	$158.66	5.720%	$167.7354	$167.74	$167.75	$167.70
Purchase #6	$39.43	5.374%	$41.549	$41.55	$41.55	$41.50
Purchase #7	$113.97	8.610%	$123.7828	$123.78	$123.80	$123.80
7 purchase totals =	$837.21		$922.1684	$922.17	$922.20	$922.10