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	$242.46	4.758%	$253.9962	$254.00	$254.00	$254.00
Purchase #2	$80.55	9.807%	$88.4495	$88.45	$88.45	$88.40
Purchase #3	$247.84	4.630%	$259.315	$259.32	$259.30	$259.30
Purchase #4	$65.72	10.808%	$72.823	$72.82	$72.80	$72.80
Purchase #5	$78.26	6.423%	$83.2866	$83.29	$83.30	$83.30
Purchase #6	$175.49	4.799%	$183.9118	$183.91	$183.90	$183.90
Purchase #7	$125.92	11.543%	$140.4549	$140.45	$140.45	$140.50
7 purchase totals =	$1,016.24		$1,082.2370	$1,082.24	$1,082.20	$1,082.20