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	$172.97	6.110%	$183.5385	$183.54	$183.55	$183.50
Purchase #2	$148.55	7.818%	$160.1636	$160.16	$160.15	$160.20
Purchase #3	$34.89	6.487%	$37.1533	$37.15	$37.15	$37.20
Purchase #4	$72.80	13.280%	$82.4678	$82.47	$82.45	$82.50
Purchase #5	$198.90	4.210%	$207.2737	$207.27	$207.25	$207.30
Purchase #6	$190.67	11.316%	$212.2462	$212.25	$212.25	$212.20
Purchase #7	$206.27	3.736%	$213.9762	$213.98	$214.00	$214.00
7 purchase totals =	$1,025.05		$1,096.8193	$1,096.82	$1,096.80	$1,096.90