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	$31.84	4.672%	$33.3276	$33.33	$33.35	$33.30
Purchase #2	$17.52	7.602%	$18.8519	$18.85	$18.85	$18.90
Purchase #3	$196.59	11.250%	$218.7064	$218.71	$218.70	$218.70
Purchase #4	$88.38	8.203%	$95.6298	$95.63	$95.65	$95.60
Purchase #5	$84.91	5.391%	$89.4875	$89.49	$89.50	$89.50
Purchase #6	$237.28	4.498%	$247.9529	$247.95	$247.95	$248.00
Purchase #7	$204.64	5.351%	$215.5903	$215.59	$215.60	$215.60
7 purchase totals =	$861.16		$919.5464	$919.55	$919.60	$919.60