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	$161.57	8.585%	$175.4408	$175.44	$175.45	$175.40
Purchase #2	$162.43	12.542%	$182.802	$182.80	$182.80	$182.80
Purchase #3	$208.76	12.570%	$235.0011	$235.00	$235.00	$235.00
Purchase #4	$36.99	13.486%	$41.9785	$41.98	$42.00	$42.00
Purchase #5	$63.96	13.215%	$72.4123	$72.41	$72.40	$72.40
Purchase #6	$218.30	9.192%	$238.3661	$238.37	$238.35	$238.40
Purchase #7	$151.80	7.309%	$162.8951	$162.90	$162.90	$162.90
7 purchase totals =	$1,003.81		$1,108.8959	$1,108.90	$1,108.90	$1,108.90