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	$168.88	13.481%	$191.6467	$191.65	$191.65	$191.60
Purchase #2	$185.80	5.679%	$196.3516	$196.35	$196.35	$196.40
Purchase #3	$233.44	3.186%	$240.8774	$240.88	$240.90	$240.90
Purchase #4	$163.52	10.314%	$180.3855	$180.39	$180.40	$180.40
Purchase #5	$83.98	10.144%	$92.4989	$92.50	$92.50	$92.50
Purchase #6	$222.31	10.273%	$245.1479	$245.15	$245.15	$245.10
Purchase #7	$202.25	4.548%	$211.4483	$211.45	$211.45	$211.40
7 purchase totals =	$1,260.18		$1,358.3563	$1,358.37	$1,358.40	$1,358.30