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	$171.99	3.817%	$178.5549	$178.55	$178.55	$178.60
Purchase #2	$57.71	3.173%	$59.5411	$59.54	$59.55	$59.50
Purchase #3	$164.45	6.611%	$175.3218	$175.32	$175.30	$175.30
Purchase #4	$146.61	6.490%	$156.125	$156.13	$156.15	$156.10
Purchase #5	$25.83	7.693%	$27.8171	$27.82	$27.80	$27.80
Purchase #6	$248.53	6.247%	$264.0557	$264.06	$264.05	$264.10
Purchase #7	$83.77	3.215%	$86.4632	$86.46	$86.45	$86.50
7 purchase totals =	$898.89		$947.8788	$947.88	$947.85	$947.90