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	$120.95	5.243%	$127.2914	$127.29	$127.30	$127.30
Purchase #2	$130.44	4.584%	$136.4194	$136.42	$136.40	$136.40
Purchase #3	$62.89	8.601%	$68.2992	$68.30	$68.30	$68.30
Purchase #4	$219.32	5.476%	$231.33	$231.33	$231.35	$231.30
Purchase #5	$188.69	5.374%	$198.8302	$198.83	$198.85	$198.80
Purchase #6	$130.45	7.202%	$139.845	$139.85	$139.85	$139.80
Purchase #7	$168.32	4.287%	$175.5359	$175.54	$175.55	$175.50
7 purchase totals =	$1,021.06		$1,077.5511	$1,077.56	$1,077.60	$1,077.40