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	$158.69	10.290%	$175.0192	$175.02	$175.00	$175.00
Purchase #2	$163.73	5.320%	$172.4404	$172.44	$172.45	$172.40
Purchase #3	$228.78	11.760%	$255.6845	$255.68	$255.70	$255.70
Purchase #4	$128.91	9.820%	$141.569	$141.57	$141.55	$141.60
Purchase #5	$241.42	9.696%	$264.8281	$264.83	$264.85	$264.80
Purchase #6	$5.76	9.716%	$6.3196	$6.32	$6.30	$6.30
Purchase #7	$42.86	11.605%	$47.8339	$47.83	$47.85	$47.80
7 purchase totals =	$970.15		$1,063.6947	$1,063.69	$1,063.70	$1,063.60