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	$6.68	8.476%	$7.2462	$7.25	$7.25	$7.20
Purchase #2	$168.90	3.211%	$174.3234	$174.32	$174.30	$174.30
Purchase #3	$237.47	13.263%	$268.9656	$268.97	$268.95	$269.00
Purchase #4	$238.90	8.572%	$259.3785	$259.38	$259.40	$259.40
Purchase #5	$73.87	6.723%	$78.8363	$78.84	$78.85	$78.80
Purchase #6	$118.80	10.409%	$131.1659	$131.17	$131.15	$131.20
Purchase #7	$127.54	13.383%	$144.6087	$144.61	$144.60	$144.60
7 purchase totals =	$972.16		$1,064.5246	$1,064.54	$1,064.50	$1,064.50