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	$51.81	12.473%	$58.2723	$58.27	$58.25	$58.30
Purchase #2	$214.33	4.636%	$224.2663	$224.27	$224.25	$224.30
Purchase #3	$149.92	5.705%	$158.4729	$158.47	$158.45	$158.50
Purchase #4	$98.74	12.701%	$111.281	$111.28	$111.30	$111.30
Purchase #5	$61.76	9.693%	$67.7464	$67.75	$67.75	$67.70
Purchase #6	$148.85	3.849%	$154.5792	$154.58	$154.60	$154.60
Purchase #7	$78.31	11.458%	$87.2828	$87.28	$87.30	$87.30
7 purchase totals =	$803.72		$861.9009	$861.90	$861.90	$862.00