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	$150.55	9.498%	$164.8492	$164.85	$164.85	$164.80
Purchase #2	$27.88	8.407%	$30.2239	$30.22	$30.20	$30.20
Purchase #3	$213.89	6.241%	$227.2389	$227.24	$227.25	$227.20
Purchase #4	$228.76	13.254%	$259.0799	$259.08	$259.10	$259.10
Purchase #5	$25.56	6.360%	$27.1856	$27.19	$27.20	$27.20
Purchase #6	$113.40	12.461%	$127.5308	$127.53	$127.55	$127.50
Purchase #7	$200.71	13.268%	$227.3402	$227.34	$227.35	$227.30
7 purchase totals =	$960.75		$1,063.4485	$1,063.45	$1,063.50	$1,063.30