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	$248.83	10.211%	$274.238	$274.24	$274.25	$274.20
Purchase #2	$70.32	3.616%	$72.8628	$72.86	$72.85	$72.90
Purchase #3	$121.73	5.333%	$128.2219	$128.22	$128.20	$128.20
Purchase #4	$45.94	4.463%	$47.9903	$47.99	$48.00	$48.00
Purchase #5	$210.39	4.485%	$219.826	$219.83	$219.85	$219.80
Purchase #6	$159.46	7.786%	$171.8756	$171.88	$171.90	$171.90
Purchase #7	$139.63	13.605%	$158.6267	$158.63	$158.65	$158.60
7 purchase totals =	$996.30		$1,073.6413	$1,073.65	$1,073.70	$1,073.60