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	$67.81	8.556%	$73.6118	$73.61	$73.60	$73.60
Purchase #2	$20.95	3.273%	$21.6357	$21.64	$21.65	$21.60
Purchase #3	$162.54	12.756%	$183.2736	$183.27	$183.25	$183.30
Purchase #4	$198.98	11.337%	$221.5384	$221.54	$221.55	$221.50
Purchase #5	$95.95	3.317%	$99.1327	$99.13	$99.15	$99.10
Purchase #6	$46.74	12.108%	$52.3993	$52.40	$52.40	$52.40
Purchase #7	$49.77	11.799%	$55.6424	$55.64	$55.65	$55.60
7 purchase totals =	$642.74		$707.2339	$707.23	$707.25	$707.10