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	$140.41	10.300%	$154.8722	$154.87	$154.85	$154.90
Purchase #2	$104.54	8.326%	$113.244	$113.24	$113.25	$113.20
Purchase #3	$118.33	7.219%	$126.8722	$126.87	$126.85	$126.90
Purchase #4	$214.42	3.662%	$222.2721	$222.27	$222.25	$222.30
Purchase #5	$198.25	11.230%	$220.5135	$220.51	$220.50	$220.50
Purchase #6	$91.91	8.495%	$99.7178	$99.72	$99.70	$99.70
Purchase #7	$94.90	6.399%	$100.9727	$100.97	$100.95	$101.00
7 purchase totals =	$962.76		$1,038.4645	$1,038.45	$1,038.35	$1,038.50