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	$137.52	13.555%	$156.1608	$156.16	$156.15	$156.20
Purchase #2	$67.85	6.712%	$72.4041	$72.40	$72.40	$72.40
Purchase #3	$213.69	13.518%	$242.5766	$242.58	$242.60	$242.60
Purchase #4	$95.75	10.415%	$105.7224	$105.72	$105.70	$105.70
Purchase #5	$189.42	6.713%	$202.1358	$202.14	$202.15	$202.10
Purchase #6	$111.27	12.682%	$125.3813	$125.38	$125.40	$125.40
Purchase #7	$166.43	10.107%	$183.2511	$183.25	$183.25	$183.30
7 purchase totals =	$981.93		$1,087.6321	$1,087.63	$1,087.65	$1,087.70