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	$152.60	9.759%	$167.4922	$167.49	$167.50	$167.50
Purchase #2	$58.89	9.503%	$64.4863	$64.49	$64.50	$64.50
Purchase #3	$164.85	4.809%	$172.7776	$172.78	$172.80	$172.80
Purchase #4	$23.27	4.582%	$24.3362	$24.34	$24.35	$24.30
Purchase #5	$165.31	12.226%	$185.5208	$185.52	$185.50	$185.50
Purchase #6	$178.50	5.359%	$188.0658	$188.07	$188.05	$188.10
Purchase #7	$180.56	7.829%	$194.696	$194.70	$194.70	$194.70
7 purchase totals =	$923.98		$997.3749	$997.39	$997.40	$997.40