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	$220.99	12.362%	$248.3088	$248.31	$248.30	$248.30
Purchase #2	$150.96	9.601%	$165.4537	$165.45	$165.45	$165.50
Purchase #3	$86.32	5.515%	$91.0805	$91.08	$91.10	$91.10
Purchase #4	$51.63	7.615%	$55.5616	$55.56	$55.55	$55.60
Purchase #5	$143.38	11.474%	$159.8314	$159.83	$159.85	$159.80
Purchase #6	$143.40	3.138%	$147.8999	$147.90	$147.90	$147.90
Purchase #7	$138.67	13.647%	$157.5943	$157.59	$157.60	$157.60
7 purchase totals =	$935.35		$1,025.7302	$1,025.72	$1,025.75	$1,025.80