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	$147.54	11.285%	$164.1899	$164.19	$164.20	$164.20
Purchase #2	$135.32	13.790%	$153.9806	$153.98	$154.00	$154.00
Purchase #3	$137.48	11.181%	$152.8516	$152.85	$152.85	$152.90
Purchase #4	$25.99	7.516%	$27.9434	$27.94	$27.95	$27.90
Purchase #5	$234.42	3.738%	$243.1826	$243.18	$243.20	$243.20
Purchase #6	$140.46	7.177%	$150.5408	$150.54	$150.55	$150.50
Purchase #7	$247.37	7.322%	$265.4824	$265.48	$265.50	$265.50
7 purchase totals =	$1,068.58		$1,158.1713	$1,158.16	$1,158.25	$1,158.20