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	$114.47	4.225%	$119.3064	$119.31	$119.30	$119.30
Purchase #2	$135.26	6.479%	$144.0235	$144.02	$144.00	$144.00
Purchase #3	$147.75	12.203%	$165.7799	$165.78	$165.80	$165.80
Purchase #4	$182.32	7.637%	$196.2438	$196.24	$196.25	$196.20
Purchase #5	$96.37	5.623%	$101.7889	$101.79	$101.80	$101.80
Purchase #6	$59.77	8.870%	$65.0716	$65.07	$65.05	$65.10
Purchase #7	$145.90	11.166%	$162.1912	$162.19	$162.20	$162.20
7 purchase totals =	$881.84		$954.4053	$954.40	$954.40	$954.40