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	$168.36	4.433%	$175.8234	$175.82	$175.80	$175.80
Purchase #2	$80.53	12.405%	$90.5197	$90.52	$90.50	$90.50
Purchase #3	$173.92	13.122%	$196.7418	$196.74	$196.75	$196.70
Purchase #4	$206.81	6.189%	$219.6095	$219.61	$219.60	$219.60
Purchase #5	$228.99	5.707%	$242.0585	$242.06	$242.05	$242.10
Purchase #6	$37.54	13.722%	$42.6912	$42.69	$42.70	$42.70
Purchase #7	$148.76	6.638%	$158.6347	$158.63	$158.65	$158.60
7 purchase totals =	$1,044.91		$1,126.0788	$1,126.07	$1,126.05	$1,126.00