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	$45.34	9.870%	$49.8151	$49.82	$49.80	$49.80
Purchase #2	$248.94	7.607%	$267.8769	$267.88	$267.90	$267.90
Purchase #3	$89.47	6.409%	$95.2041	$95.20	$95.20	$95.20
Purchase #4	$184.47	5.350%	$194.3391	$194.34	$194.35	$194.30
Purchase #5	$70.55	11.150%	$78.4163	$78.42	$78.40	$78.40
Purchase #6	$206.27	6.363%	$219.395	$219.40	$219.40	$219.40
Purchase #7	$131.35	8.574%	$142.6119	$142.61	$142.60	$142.60
7 purchase totals =	$976.39		$1,047.6584	$1,047.67	$1,047.65	$1,047.60