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	$161.92	3.143%	$167.0091	$167.01	$167.00	$167.00
Purchase #2	$186.65	5.151%	$196.2643	$196.26	$196.25	$196.30
Purchase #3	$53.47	10.769%	$59.2282	$59.23	$59.25	$59.20
Purchase #4	$218.89	7.562%	$235.4425	$235.44	$235.45	$235.40
Purchase #5	$215.74	12.152%	$241.9567	$241.96	$241.95	$242.00
Purchase #6	$39.44	8.680%	$42.8634	$42.86	$42.85	$42.90
Purchase #7	$130.89	5.421%	$137.9855	$137.99	$138.00	$138.00
7 purchase totals =	$1,007.00		$1,080.7497	$1,080.75	$1,080.75	$1,080.80