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	$85.46	10.110%	$94.1	$94.10	$94.10	$94.10
Purchase #2	$98.32	13.439%	$111.5332	$111.53	$111.55	$111.50
Purchase #3	$107.47	8.533%	$116.6404	$116.64	$116.65	$116.60
Purchase #4	$73.73	10.510%	$81.479	$81.48	$81.50	$81.50
Purchase #5	$230.68	8.514%	$250.3201	$250.32	$250.30	$250.30
Purchase #6	$238.75	13.304%	$270.5133	$270.51	$270.50	$270.50
Purchase #7	$64.30	5.418%	$67.7838	$67.78	$67.80	$67.80
7 purchase totals =	$898.71		$992.3698	$992.36	$992.40	$992.30