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	$239.94	10.369%	$264.8194	$264.82	$264.80	$264.80
Purchase #2	$198.30	10.307%	$218.7388	$218.74	$218.75	$218.70
Purchase #3	$161.29	11.353%	$179.6013	$179.60	$179.60	$179.60
Purchase #4	$113.68	8.836%	$123.7248	$123.72	$123.70	$123.70
Purchase #5	$46.67	8.562%	$50.6659	$50.67	$50.65	$50.70
Purchase #6	$94.88	5.730%	$100.3166	$100.32	$100.30	$100.30
Purchase #7	$112.38	10.704%	$124.4092	$124.41	$124.40	$124.40
7 purchase totals =	$967.14		$1,062.2760	$1,062.28	$1,062.20	$1,062.20