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	$229.76	12.741%	$259.0337	$259.03	$259.05	$259.00
Purchase #2	$65.66	12.417%	$73.813	$73.81	$73.80	$73.80
Purchase #3	$132.83	5.857%	$140.6099	$140.61	$140.60	$140.60
Purchase #4	$114.35	7.687%	$123.1401	$123.14	$123.15	$123.10
Purchase #5	$142.84	6.711%	$152.426	$152.43	$152.45	$152.40
Purchase #6	$183.74	7.782%	$198.0386	$198.04	$198.05	$198.00
Purchase #7	$80.92	5.414%	$85.301	$85.30	$85.30	$85.30
7 purchase totals =	$950.10		$1,032.3623	$1,032.36	$1,032.40	$1,032.20