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	$211.98	12.171%	$237.7801	$237.78	$237.80	$237.80
Purchase #2	$126.74	13.196%	$143.4646	$143.46	$143.45	$143.50
Purchase #3	$248.56	4.110%	$258.7758	$258.78	$258.80	$258.80
Purchase #4	$245.29	13.112%	$277.4524	$277.45	$277.45	$277.50
Purchase #5	$11.55	7.449%	$12.4104	$12.41	$12.40	$12.40
Purchase #6	$63.38	3.612%	$65.6693	$65.67	$65.65	$65.70
Purchase #7	$97.30	12.677%	$109.6347	$109.63	$109.65	$109.60
7 purchase totals =	$1,004.80		$1,105.1873	$1,105.18	$1,105.20	$1,105.30