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	$221.64	8.442%	$240.3508	$240.35	$240.35	$240.40
Purchase #2	$89.49	6.380%	$95.1995	$95.20	$95.20	$95.20
Purchase #3	$158.64	4.387%	$165.5995	$165.60	$165.60	$165.60
Purchase #4	$100.67	3.174%	$103.8653	$103.87	$103.85	$103.90
Purchase #5	$165.45	13.326%	$187.4979	$187.50	$187.50	$187.50
Purchase #6	$115.26	12.788%	$129.9994	$130.00	$130.00	$130.00
Purchase #7	$72.31	9.805%	$79.4	$79.40	$79.40	$79.40
7 purchase totals =	$923.46		$1,001.9124	$1,001.92	$1,001.90	$1,002.00