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	$93.76	10.768%	$103.8561	$103.86	$103.85	$103.90
Purchase #2	$118.80	10.357%	$131.1041	$131.10	$131.10	$131.10
Purchase #3	$156.32	8.711%	$169.937	$169.94	$169.95	$169.90
Purchase #4	$175.48	9.288%	$191.7786	$191.78	$191.80	$191.80
Purchase #5	$152.80	6.227%	$162.3149	$162.31	$162.30	$162.30
Purchase #6	$105.30	6.735%	$112.392	$112.39	$112.40	$112.40
Purchase #7	$121.54	4.294%	$126.7589	$126.76	$126.75	$126.80
7 purchase totals =	$924.00		$998.1416	$998.14	$998.15	$998.20