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	$133.29	8.800%	$145.0195	$145.02	$145.00	$145.00
Purchase #2	$59.33	8.790%	$64.5451	$64.55	$64.55	$64.50
Purchase #3	$240.57	6.475%	$256.1469	$256.15	$256.15	$256.10
Purchase #4	$209.39	11.576%	$233.629	$233.63	$233.65	$233.60
Purchase #5	$223.52	6.183%	$237.3402	$237.34	$237.35	$237.30
Purchase #6	$169.63	5.262%	$178.5559	$178.56	$178.55	$178.60
Purchase #7	$31.27	11.863%	$34.9796	$34.98	$35.00	$35.00
7 purchase totals =	$1,067.00		$1,150.2162	$1,150.23	$1,150.25	$1,150.10