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	$139.25	3.802%	$144.5443	$144.54	$144.55	$144.50
Purchase #2	$35.77	3.589%	$37.0538	$37.05	$37.05	$37.10
Purchase #3	$237.55	4.632%	$248.5533	$248.55	$248.55	$248.60
Purchase #4	$34.80	4.609%	$36.4039	$36.40	$36.40	$36.40
Purchase #5	$198.50	6.597%	$211.595	$211.60	$211.60	$211.60
Purchase #6	$155.33	6.775%	$165.8536	$165.85	$165.85	$165.90
Purchase #7	$31.65	4.646%	$33.1205	$33.12	$33.10	$33.10
7 purchase totals =	$832.85		$877.1244	$877.11	$877.10	$877.20