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	$111.72	7.705%	$120.328	$120.33	$120.35	$120.30
Purchase #2	$33.77	5.352%	$35.5774	$35.58	$35.60	$35.60
Purchase #3	$152.72	7.817%	$164.6581	$164.66	$164.65	$164.70
Purchase #4	$169.75	5.229%	$178.6262	$178.63	$178.65	$178.60
Purchase #5	$199.28	6.499%	$212.2312	$212.23	$212.25	$212.20
Purchase #6	$86.61	13.724%	$98.4964	$98.50	$98.50	$98.50
Purchase #7	$180.93	5.818%	$191.4565	$191.46	$191.45	$191.50
7 purchase totals =	$934.78		$1,001.3738	$1,001.39	$1,001.45	$1,001.40