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	$17.61	9.523%	$19.287	$19.29	$19.30	$19.30
Purchase #2	$159.38	12.210%	$178.8403	$178.84	$178.85	$178.80
Purchase #3	$63.78	11.714%	$71.2512	$71.25	$71.25	$71.30
Purchase #4	$168.52	3.574%	$174.5429	$174.54	$174.55	$174.50
Purchase #5	$29.69	4.837%	$31.1261	$31.13	$31.15	$31.10
Purchase #6	$191.96	3.103%	$197.9165	$197.92	$197.90	$197.90
Purchase #7	$181.37	9.497%	$198.5947	$198.59	$198.60	$198.60
7 purchase totals =	$812.31		$871.5587	$871.56	$871.60	$871.50