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	$210.45	4.745%	$220.4359	$220.44	$220.45	$220.40
Purchase #2	$242.80	10.689%	$268.7529	$268.75	$268.75	$268.80
Purchase #3	$199.61	11.287%	$222.14	$222.14	$222.15	$222.10
Purchase #4	$84.51	6.817%	$90.271	$90.27	$90.25	$90.30
Purchase #5	$246.43	5.133%	$259.0793	$259.08	$259.10	$259.10
Purchase #6	$103.96	10.184%	$114.5473	$114.55	$114.55	$114.50
Purchase #7	$33.42	11.847%	$37.3793	$37.38	$37.40	$37.40
7 purchase totals =	$1,121.18		$1,212.6057	$1,212.61	$1,212.65	$1,212.60