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	$229.85	8.735%	$249.9274	$249.93	$249.95	$249.90
Purchase #2	$101.52	7.602%	$109.2376	$109.24	$109.25	$109.20
Purchase #3	$41.31	12.412%	$46.4374	$46.44	$46.45	$46.40
Purchase #4	$104.98	11.345%	$116.89	$116.89	$116.90	$116.90
Purchase #5	$248.58	9.673%	$272.6251	$272.63	$272.65	$272.60
Purchase #6	$168.31	7.474%	$180.8895	$180.89	$180.90	$180.90
Purchase #7	$134.91	9.228%	$147.3595	$147.36	$147.35	$147.40
7 purchase totals =	$1,029.46		$1,123.3665	$1,123.38	$1,123.45	$1,123.30