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	$175.93	5.693%	$185.9457	$185.95	$185.95	$185.90
Purchase #2	$176.34	4.601%	$184.4534	$184.45	$184.45	$184.50
Purchase #3	$221.78	12.176%	$248.7839	$248.78	$248.80	$248.80
Purchase #4	$200.57	7.605%	$215.8233	$215.82	$215.80	$215.80
Purchase #5	$96.45	13.224%	$109.2045	$109.20	$109.20	$109.20
Purchase #6	$81.47	4.424%	$85.0742	$85.07	$85.05	$85.10
Purchase #7	$109.51	9.219%	$119.6057	$119.61	$119.60	$119.60
7 purchase totals =	$1,062.05		$1,148.8907	$1,148.88	$1,148.85	$1,148.90