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	$142.27	5.450%	$150.0237	$150.02	$150.00	$150.00
Purchase #2	$161.83	8.445%	$175.4965	$175.50	$175.50	$175.50
Purchase #3	$197.32	11.366%	$219.7474	$219.75	$219.75	$219.70
Purchase #4	$40.54	12.375%	$45.5568	$45.56	$45.55	$45.60
Purchase #5	$197.51	4.545%	$206.4868	$206.49	$206.50	$206.50
Purchase #6	$219.33	12.140%	$245.9567	$245.96	$245.95	$246.00
Purchase #7	$160.43	11.641%	$179.1057	$179.11	$179.10	$179.10
7 purchase totals =	$1,119.23		$1,222.3736	$1,222.39	$1,222.35	$1,222.40