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	$248.40	3.873%	$258.0205	$258.02	$258.00	$258.00
Purchase #2	$81.44	10.750%	$90.1948	$90.19	$90.20	$90.20
Purchase #3	$150.40	3.839%	$156.1739	$156.17	$156.15	$156.20
Purchase #4	$97.39	3.473%	$100.7724	$100.77	$100.75	$100.80
Purchase #5	$233.62	6.576%	$248.9829	$248.98	$249.00	$249.00
Purchase #6	$168.77	7.228%	$180.9687	$180.97	$180.95	$181.00
Purchase #7	$34.37	8.697%	$37.3592	$37.36	$37.35	$37.40
7 purchase totals =	$1,014.39		$1,072.4724	$1,072.46	$1,072.40	$1,072.60