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	$75.42	8.861%	$82.103	$82.10	$82.10	$82.10
Purchase #2	$54.37	12.653%	$61.2494	$61.25	$61.25	$61.20
Purchase #3	$200.72	6.134%	$213.0322	$213.03	$213.05	$213.00
Purchase #4	$111.29	11.292%	$123.8569	$123.86	$123.85	$123.90
Purchase #5	$231.76	7.480%	$249.0956	$249.10	$249.10	$249.10
Purchase #6	$167.98	10.257%	$185.2097	$185.21	$185.20	$185.20
Purchase #7	$135.50	6.544%	$144.3671	$144.37	$144.35	$144.40
7 purchase totals =	$977.04		$1,058.9139	$1,058.92	$1,058.90	$1,058.90