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	$132.43	9.214%	$144.6321	$144.63	$144.65	$144.60
Purchase #2	$247.91	6.387%	$263.744	$263.74	$263.75	$263.70
Purchase #3	$121.56	8.225%	$131.5583	$131.56	$131.55	$131.60
Purchase #4	$125.34	13.592%	$142.3762	$142.38	$142.40	$142.40
Purchase #5	$228.92	13.147%	$259.0161	$259.02	$259.00	$259.00
Purchase #6	$92.69	11.302%	$103.1658	$103.17	$103.15	$103.20
Purchase #7	$57.51	13.216%	$65.1105	$65.11	$65.10	$65.10
7 purchase totals =	$1,006.36		$1,109.6030	$1,109.61	$1,109.60	$1,109.60