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	$95.59	7.629%	$102.8826	$102.88	$102.90	$102.90
Purchase #2	$188.98	5.380%	$199.1471	$199.15	$199.15	$199.10
Purchase #3	$246.60	4.657%	$258.0842	$258.08	$258.10	$258.10
Purchase #4	$97.30	5.670%	$102.8169	$102.82	$102.80	$102.80
Purchase #5	$220.46	3.687%	$228.5884	$228.59	$228.60	$228.60
Purchase #6	$106.61	6.696%	$113.7486	$113.75	$113.75	$113.70
Purchase #7	$67.83	5.643%	$71.6576	$71.66	$71.65	$71.70
7 purchase totals =	$1,023.37		$1,076.9254	$1,076.93	$1,076.95	$1,076.90