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	$164.48	10.323%	$181.4593	$181.46	$181.45	$181.50
Purchase #2	$141.79	4.179%	$147.7154	$147.72	$147.70	$147.70
Purchase #3	$56.75	5.644%	$59.953	$59.95	$59.95	$60.00
Purchase #4	$109.93	11.394%	$122.4554	$122.46	$122.45	$122.50
Purchase #5	$133.40	8.144%	$144.2641	$144.26	$144.25	$144.30
Purchase #6	$39.44	8.341%	$42.7297	$42.73	$42.75	$42.70
Purchase #7	$80.86	6.836%	$86.3876	$86.39	$86.40	$86.40
7 purchase totals =	$726.65		$784.9645	$784.97	$784.95	$785.10