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	$193.68	10.603%	$214.2159	$214.22	$214.20	$214.20
Purchase #2	$27.75	5.797%	$29.3587	$29.36	$29.35	$29.40
Purchase #3	$151.69	7.103%	$162.4645	$162.46	$162.45	$162.50
Purchase #4	$223.91	9.587%	$245.3763	$245.38	$245.40	$245.40
Purchase #5	$192.38	9.399%	$210.4618	$210.46	$210.45	$210.50
Purchase #6	$38.33	5.156%	$40.3063	$40.31	$40.30	$40.30
Purchase #7	$148.48	4.493%	$155.1512	$155.15	$155.15	$155.20
7 purchase totals =	$976.22		$1,057.3347	$1,057.34	$1,057.30	$1,057.50