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	$162.69	4.254%	$169.6108	$169.61	$169.60	$169.60
Purchase #2	$16.61	13.815%	$18.9047	$18.90	$18.90	$18.90
Purchase #3	$90.28	10.360%	$99.633	$99.63	$99.65	$99.60
Purchase #4	$206.46	10.635%	$228.417	$228.42	$228.40	$228.40
Purchase #5	$86.48	10.316%	$95.4013	$95.40	$95.40	$95.40
Purchase #6	$37.92	13.298%	$42.9626	$42.96	$42.95	$43.00
Purchase #7	$214.36	12.383%	$240.9042	$240.90	$240.90	$240.90
7 purchase totals =	$814.80		$895.8336	$895.82	$895.80	$895.80