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	$165.93	9.263%	$181.3001	$181.30	$181.30	$181.30
Purchase #2	$145.69	10.425%	$160.8782	$160.88	$160.90	$160.90
Purchase #3	$59.88	8.421%	$64.9225	$64.92	$64.90	$64.90
Purchase #4	$105.89	3.629%	$109.7327	$109.73	$109.75	$109.70
Purchase #5	$34.75	8.149%	$37.5818	$37.58	$37.60	$37.60
Purchase #6	$152.52	10.398%	$168.379	$168.38	$168.40	$168.40
Purchase #7	$118.43	11.788%	$132.3905	$132.39	$132.40	$132.40
7 purchase totals =	$783.09		$855.1848	$855.18	$855.25	$855.20