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	$244.65	5.807%	$258.8568	$258.86	$258.85	$258.90
Purchase #2	$179.58	3.792%	$186.3897	$186.39	$186.40	$186.40
Purchase #3	$71.88	9.146%	$78.4541	$78.45	$78.45	$78.50
Purchase #4	$118.82	7.650%	$127.9097	$127.91	$127.90	$127.90
Purchase #5	$189.39	4.713%	$198.316	$198.32	$198.30	$198.30
Purchase #6	$124.98	6.799%	$133.4774	$133.48	$133.50	$133.50
Purchase #7	$125.58	8.216%	$135.8977	$135.90	$135.90	$135.90
7 purchase totals =	$1,054.88		$1,119.3014	$1,119.31	$1,119.30	$1,119.40