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	$91.73	3.873%	$95.2827	$95.28	$95.30	$95.30
Purchase #2	$125.55	13.520%	$142.5244	$142.52	$142.50	$142.50
Purchase #3	$91.83	12.236%	$103.0663	$103.07	$103.05	$103.10
Purchase #4	$141.96	3.659%	$147.1543	$147.15	$147.15	$147.20
Purchase #5	$207.52	4.640%	$217.1489	$217.15	$217.15	$217.10
Purchase #6	$165.38	5.245%	$174.0542	$174.05	$174.05	$174.10
Purchase #7	$66.59	7.683%	$71.7061	$71.71	$71.70	$71.70
7 purchase totals =	$890.56		$950.9369	$950.93	$950.90	$951.00