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	$231.56	4.418%	$241.7903	$241.79	$241.80	$241.80
Purchase #2	$104.48	11.489%	$116.4837	$116.48	$116.50	$116.50
Purchase #3	$126.41	5.814%	$133.7595	$133.76	$133.75	$133.80
Purchase #4	$135.86	12.867%	$153.3411	$153.34	$153.35	$153.30
Purchase #5	$127.89	13.429%	$145.0643	$145.06	$145.05	$145.10
Purchase #6	$39.97	12.235%	$44.8603	$44.86	$44.85	$44.90
Purchase #7	$158.59	6.531%	$168.9475	$168.95	$168.95	$168.90
7 purchase totals =	$924.76		$1,004.2467	$1,004.24	$1,004.25	$1,004.30