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	$206.43	4.506%	$215.7317	$215.73	$215.75	$215.70
Purchase #2	$139.74	5.416%	$147.3083	$147.31	$147.30	$147.30
Purchase #3	$90.77	13.517%	$103.0394	$103.04	$103.05	$103.00
Purchase #4	$121.42	9.712%	$133.2123	$133.21	$133.20	$133.20
Purchase #5	$124.79	5.477%	$131.6247	$131.62	$131.60	$131.60
Purchase #6	$158.47	4.308%	$165.2969	$165.30	$165.30	$165.30
Purchase #7	$98.44	11.299%	$109.5627	$109.56	$109.55	$109.60
7 purchase totals =	$940.06		$1,005.7760	$1,005.77	$1,005.75	$1,005.70