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	$228.66	5.794%	$241.9086	$241.91	$241.90	$241.90
Purchase #2	$175.25	7.581%	$188.5357	$188.54	$188.55	$188.50
Purchase #3	$164.72	12.620%	$185.5077	$185.51	$185.50	$185.50
Purchase #4	$174.42	13.674%	$198.2702	$198.27	$198.25	$198.30
Purchase #5	$199.47	7.243%	$213.9176	$213.92	$213.90	$213.90
Purchase #6	$218.77	10.353%	$241.4193	$241.42	$241.40	$241.40
Purchase #7	$59.59	4.465%	$62.2507	$62.25	$62.25	$62.30
7 purchase totals =	$1,220.88		$1,331.8098	$1,331.82	$1,331.75	$1,331.80