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	$172.78	4.270%	$180.1577	$180.16	$180.15	$180.20
Purchase #2	$43.80	4.807%	$45.9055	$45.91	$45.90	$45.90
Purchase #3	$169.25	4.185%	$176.3331	$176.33	$176.35	$176.30
Purchase #4	$174.68	9.611%	$191.4685	$191.47	$191.45	$191.50
Purchase #5	$240.27	5.792%	$254.1864	$254.19	$254.20	$254.20
Purchase #6	$137.62	9.459%	$150.6375	$150.64	$150.65	$150.60
Purchase #7	$5.95	7.580%	$6.401	$6.40	$6.40	$6.40
7 purchase totals =	$944.35		$1,005.0897	$1,005.10	$1,005.10	$1,005.10