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	$51.59	4.382%	$53.8507	$53.85	$53.85	$53.90
Purchase #2	$194.50	9.542%	$213.0592	$213.06	$213.05	$213.10
Purchase #3	$234.59	13.697%	$266.7218	$266.72	$266.70	$266.70
Purchase #4	$118.72	7.518%	$127.6454	$127.65	$127.65	$127.60
Purchase #5	$174.36	8.138%	$188.5494	$188.55	$188.55	$188.50
Purchase #6	$54.46	7.319%	$58.4459	$58.45	$58.45	$58.40
Purchase #7	$120.88	5.783%	$127.8705	$127.87	$127.85	$127.90
7 purchase totals =	$949.10		$1,036.1429	$1,036.15	$1,036.10	$1,036.10