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	$70.30	13.218%	$79.5923	$79.59	$79.60	$79.60
Purchase #2	$109.73	6.644%	$117.0205	$117.02	$117.00	$117.00
Purchase #3	$179.30	9.340%	$196.0466	$196.05	$196.05	$196.00
Purchase #4	$64.39	4.742%	$67.4434	$67.44	$67.45	$67.40
Purchase #5	$189.98	5.758%	$200.919	$200.92	$200.90	$200.90
Purchase #6	$14.38	5.183%	$15.1253	$15.13	$15.15	$15.10
Purchase #7	$68.27	3.815%	$70.8745	$70.87	$70.85	$70.90
7 purchase totals =	$696.35		$747.0216	$747.02	$747.00	$746.90