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	$152.37	9.864%	$167.3998	$167.40	$167.40	$167.40
Purchase #2	$198.86	6.834%	$212.4501	$212.45	$212.45	$212.50
Purchase #3	$12.97	6.151%	$13.7678	$13.77	$13.75	$13.80
Purchase #4	$230.64	10.759%	$255.4546	$255.45	$255.45	$255.50
Purchase #5	$26.71	10.573%	$29.534	$29.53	$29.55	$29.50
Purchase #6	$39.89	3.786%	$41.4002	$41.40	$41.40	$41.40
Purchase #7	$32.40	4.115%	$33.7333	$33.73	$33.75	$33.70
7 purchase totals =	$693.84		$753.7398	$753.73	$753.75	$753.80