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	$237.95	6.451%	$253.3002	$253.30	$253.30	$253.30
Purchase #2	$41.33	12.734%	$46.593	$46.59	$46.60	$46.60
Purchase #3	$134.43	8.841%	$146.315	$146.32	$146.30	$146.30
Purchase #4	$176.28	3.110%	$181.7623	$181.76	$181.75	$181.80
Purchase #5	$80.40	6.695%	$85.7828	$85.78	$85.80	$85.80
Purchase #6	$117.89	10.558%	$130.3368	$130.34	$130.35	$130.30
Purchase #7	$86.29	3.558%	$89.3602	$89.36	$89.35	$89.40
7 purchase totals =	$874.57		$933.4503	$933.45	$933.45	$933.50