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	$52.29	8.684%	$56.8309	$56.83	$56.85	$56.80
Purchase #2	$162.96	11.229%	$181.2588	$181.26	$181.25	$181.30
Purchase #3	$19.91	7.690%	$21.4411	$21.44	$21.45	$21.40
Purchase #4	$86.31	3.146%	$89.0253	$89.03	$89.05	$89.00
Purchase #5	$100.62	9.196%	$109.873	$109.87	$109.85	$109.90
Purchase #6	$69.87	7.234%	$74.9244	$74.92	$74.90	$74.90
Purchase #7	$158.32	5.467%	$166.9754	$166.98	$167.00	$167.00
7 purchase totals =	$650.28		$700.3289	$700.33	$700.35	$700.30