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	$130.33	4.723%	$136.4855	$136.49	$136.50	$136.50
Purchase #2	$218.77	3.706%	$226.8776	$226.88	$226.90	$226.90
Purchase #3	$170.65	11.470%	$190.2236	$190.22	$190.20	$190.20
Purchase #4	$58.32	12.121%	$65.389	$65.39	$65.40	$65.40
Purchase #5	$112.61	5.568%	$118.8801	$118.88	$118.90	$118.90
Purchase #6	$134.69	4.752%	$141.0905	$141.09	$141.10	$141.10
Purchase #7	$161.95	6.147%	$171.9051	$171.91	$171.90	$171.90
7 purchase totals =	$987.32		$1,050.8514	$1,050.86	$1,050.90	$1,050.90