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	$59.72	3.715%	$61.9386	$61.94	$61.95	$61.90
Purchase #2	$199.48	9.323%	$218.0775	$218.08	$218.10	$218.10
Purchase #3	$241.81	10.271%	$266.6463	$266.65	$266.65	$266.60
Purchase #4	$88.89	11.181%	$98.8288	$98.83	$98.85	$98.80
Purchase #5	$43.38	4.419%	$45.297	$45.30	$45.30	$45.30
Purchase #6	$172.36	4.746%	$180.5402	$180.54	$180.55	$180.50
Purchase #7	$220.53	3.169%	$227.5186	$227.52	$227.50	$227.50
7 purchase totals =	$1,026.17		$1,098.8470	$1,098.86	$1,098.90	$1,098.70