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	$191.96	11.398%	$213.8396	$213.84	$213.85	$213.80
Purchase #2	$232.86	12.190%	$261.2456	$261.25	$261.25	$261.20
Purchase #3	$147.70	12.139%	$165.6293	$165.63	$165.65	$165.60
Purchase #4	$110.93	3.319%	$114.6118	$114.61	$114.60	$114.60
Purchase #5	$35.66	6.450%	$37.9601	$37.96	$37.95	$38.00
Purchase #6	$99.94	13.456%	$113.3879	$113.39	$113.40	$113.40
Purchase #7	$164.47	10.556%	$181.8315	$181.83	$181.85	$181.80
7 purchase totals =	$983.52		$1,088.5058	$1,088.51	$1,088.55	$1,088.40