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	$133.76	7.396%	$143.6529	$143.65	$143.65	$143.70
Purchase #2	$54.90	13.240%	$62.1688	$62.17	$62.15	$62.20
Purchase #3	$206.38	4.112%	$214.8663	$214.87	$214.85	$214.90
Purchase #4	$162.65	3.868%	$168.9413	$168.94	$168.95	$168.90
Purchase #5	$83.41	12.795%	$94.0823	$94.08	$94.10	$94.10
Purchase #6	$148.41	12.756%	$167.3412	$167.34	$167.35	$167.30
Purchase #7	$37.57	7.549%	$40.4062	$40.41	$40.40	$40.40
7 purchase totals =	$827.08		$891.4590	$891.46	$891.45	$891.50