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	$163.83	9.447%	$179.307	$179.31	$179.30	$179.30
Purchase #2	$71.84	11.314%	$79.968	$79.97	$79.95	$80.00
Purchase #3	$241.39	13.194%	$273.239	$273.24	$273.25	$273.20
Purchase #4	$31.72	4.222%	$33.0592	$33.06	$33.05	$33.10
Purchase #5	$55.47	3.390%	$57.3504	$57.35	$57.35	$57.40
Purchase #6	$54.52	9.415%	$59.6531	$59.65	$59.65	$59.70
Purchase #7	$66.33	5.166%	$69.7566	$69.76	$69.75	$69.80
7 purchase totals =	$685.10		$752.3333	$752.34	$752.30	$752.50