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	$38.46	10.839%	$42.6287	$42.63	$42.65	$42.60
Purchase #2	$135.26	4.614%	$141.5009	$141.50	$141.50	$141.50
Purchase #3	$185.35	3.336%	$191.5333	$191.53	$191.55	$191.50
Purchase #4	$23.31	4.224%	$24.2946	$24.29	$24.30	$24.30
Purchase #5	$102.89	3.445%	$106.4346	$106.43	$106.45	$106.40
Purchase #6	$119.40	3.422%	$123.4859	$123.49	$123.50	$123.50
Purchase #7	$191.70	13.481%	$217.5431	$217.54	$217.55	$217.50
7 purchase totals =	$796.37		$847.4211	$847.41	$847.50	$847.30