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	$208.41	7.212%	$223.4405	$223.44	$223.45	$223.40
Purchase #2	$167.32	10.302%	$184.5573	$184.56	$184.55	$184.60
Purchase #3	$136.38	5.678%	$144.1237	$144.12	$144.10	$144.10
Purchase #4	$180.38	10.251%	$198.8708	$198.87	$198.85	$198.90
Purchase #5	$228.99	3.482%	$236.9634	$236.96	$236.95	$237.00
Purchase #6	$103.84	7.153%	$111.2677	$111.27	$111.25	$111.30
Purchase #7	$109.42	12.789%	$123.4137	$123.41	$123.40	$123.40
7 purchase totals =	$1,134.74		$1,222.6371	$1,222.63	$1,222.55	$1,222.70