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	$51.50	5.615%	$54.3917	$54.39	$54.40	$54.40
Purchase #2	$218.30	9.211%	$238.4076	$238.41	$238.40	$238.40
Purchase #3	$145.84	12.763%	$164.4536	$164.45	$164.45	$164.50
Purchase #4	$163.83	6.552%	$174.5641	$174.56	$174.55	$174.60
Purchase #5	$155.26	9.254%	$169.6278	$169.63	$169.65	$169.60
Purchase #6	$146.90	5.590%	$155.1117	$155.11	$155.10	$155.10
Purchase #7	$145.97	6.805%	$155.9033	$155.90	$155.90	$155.90
7 purchase totals =	$1,027.60		$1,112.4598	$1,112.45	$1,112.45	$1,112.50