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	$220.35	5.123%	$231.6385	$231.64	$231.65	$231.60
Purchase #2	$49.93	4.188%	$52.0211	$52.02	$52.00	$52.00
Purchase #3	$38.82	9.572%	$42.5359	$42.54	$42.55	$42.50
Purchase #4	$196.78	9.729%	$215.9247	$215.92	$215.90	$215.90
Purchase #5	$13.72	7.414%	$14.7372	$14.74	$14.75	$14.70
Purchase #6	$117.85	10.728%	$130.4929	$130.49	$130.50	$130.50
Purchase #7	$150.77	12.512%	$169.6343	$169.63	$169.65	$169.60
7 purchase totals =	$788.22		$856.9846	$856.98	$857.00	$856.80