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	$95.44	5.871%	$101.0433	$101.04	$101.05	$101.00
Purchase #2	$179.65	9.543%	$196.794	$196.79	$196.80	$196.80
Purchase #3	$56.26	9.477%	$61.5918	$61.59	$61.60	$61.60
Purchase #4	$239.54	5.710%	$253.2177	$253.22	$253.20	$253.20
Purchase #5	$243.83	5.615%	$257.5211	$257.52	$257.50	$257.50
Purchase #6	$212.61	4.613%	$222.4177	$222.42	$222.40	$222.40
Purchase #7	$174.36	6.299%	$185.3429	$185.34	$185.35	$185.30
7 purchase totals =	$1,201.69		$1,277.9285	$1,277.92	$1,277.90	$1,277.80