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	$179.55	5.367%	$189.1864	$189.19	$189.20	$189.20
Purchase #2	$214.68	6.348%	$228.3079	$228.31	$228.30	$228.30
Purchase #3	$88.39	13.488%	$100.312	$100.31	$100.30	$100.30
Purchase #4	$97.90	11.704%	$109.3582	$109.36	$109.35	$109.40
Purchase #5	$155.40	4.652%	$162.6292	$162.63	$162.65	$162.60
Purchase #6	$106.40	9.131%	$116.1154	$116.12	$116.10	$116.10
Purchase #7	$132.78	11.752%	$148.3843	$148.38	$148.40	$148.40
7 purchase totals =	$975.10		$1,054.2934	$1,054.30	$1,054.30	$1,054.30