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	$41.77	9.207%	$45.6158	$45.62	$45.60	$45.60
Purchase #2	$247.35	11.792%	$276.5175	$276.52	$276.50	$276.50
Purchase #3	$188.34	6.209%	$200.034	$200.03	$200.05	$200.00
Purchase #4	$243.54	10.297%	$268.6173	$268.62	$268.60	$268.60
Purchase #5	$64.38	11.597%	$71.8461	$71.85	$71.85	$71.80
Purchase #6	$168.78	3.276%	$174.3092	$174.31	$174.30	$174.30
Purchase #7	$34.89	10.278%	$38.476	$38.48	$38.50	$38.50
7 purchase totals =	$989.05		$1,075.4159	$1,075.43	$1,075.40	$1,075.30