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	$249.34	8.265%	$269.948	$269.95	$269.95	$269.90
Purchase #2	$141.51	13.774%	$161.0016	$161.00	$161.00	$161.00
Purchase #3	$243.38	8.846%	$264.9094	$264.91	$264.90	$264.90
Purchase #4	$161.65	6.273%	$171.7903	$171.79	$171.80	$171.80
Purchase #5	$237.78	5.536%	$250.9435	$250.94	$250.95	$250.90
Purchase #6	$39.36	3.803%	$40.8569	$40.86	$40.85	$40.90
Purchase #7	$233.58	3.608%	$242.0076	$242.01	$242.00	$242.00
7 purchase totals =	$1,306.60		$1,401.4573	$1,401.46	$1,401.45	$1,401.40