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	$223.73	7.551%	$240.6239	$240.62	$240.60	$240.60
Purchase #2	$175.83	5.517%	$185.5305	$185.53	$185.55	$185.50
Purchase #3	$126.73	4.731%	$132.7256	$132.73	$132.75	$132.70
Purchase #4	$165.86	6.449%	$176.5563	$176.56	$176.55	$176.60
Purchase #5	$189.61	6.630%	$202.1811	$202.18	$202.20	$202.20
Purchase #6	$31.25	7.302%	$33.5319	$33.53	$33.55	$33.50
Purchase #7	$103.88	5.779%	$109.8832	$109.88	$109.90	$109.90
7 purchase totals =	$1,016.89		$1,081.0325	$1,081.03	$1,081.10	$1,081.00