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	$106.28	6.517%	$113.2063	$113.21	$113.20	$113.20
Purchase #2	$79.93	4.401%	$83.4477	$83.45	$83.45	$83.40
Purchase #3	$41.63	5.129%	$43.7652	$43.77	$43.75	$43.80
Purchase #4	$91.72	8.344%	$99.3731	$99.37	$99.35	$99.40
Purchase #5	$70.90	10.642%	$78.4452	$78.45	$78.45	$78.40
Purchase #6	$249.84	3.501%	$258.5869	$258.59	$258.60	$258.60
Purchase #7	$122.38	9.564%	$134.0844	$134.08	$134.10	$134.10
7 purchase totals =	$762.68		$810.9088	$810.92	$810.90	$810.90