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	$109.69	7.224%	$117.614	$117.61	$117.60	$117.60
Purchase #2	$55.47	3.638%	$57.488	$57.49	$57.50	$57.50
Purchase #3	$196.48	11.624%	$219.3188	$219.32	$219.30	$219.30
Purchase #4	$65.33	10.599%	$72.2543	$72.25	$72.25	$72.30
Purchase #5	$120.64	10.669%	$133.5111	$133.51	$133.50	$133.50
Purchase #6	$135.96	12.133%	$152.456	$152.46	$152.45	$152.50
Purchase #7	$131.30	3.693%	$136.1489	$136.15	$136.15	$136.10
7 purchase totals =	$814.87		$888.7911	$888.79	$888.75	$888.80