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	$197.85	8.776%	$215.2133	$215.21	$215.20	$215.20
Purchase #2	$72.42	11.785%	$80.9547	$80.95	$80.95	$81.00
Purchase #3	$145.57	7.450%	$156.415	$156.42	$156.40	$156.40
Purchase #4	$98.43	11.340%	$109.592	$109.59	$109.60	$109.60
Purchase #5	$194.59	7.440%	$209.0675	$209.07	$209.05	$209.10
Purchase #6	$119.92	6.334%	$127.5157	$127.52	$127.50	$127.50
Purchase #7	$48.58	8.351%	$52.6369	$52.64	$52.65	$52.60
7 purchase totals =	$877.36		$951.3951	$951.40	$951.35	$951.40