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	$187.26	10.870%	$207.6152	$207.62	$207.60	$207.60
Purchase #2	$6.65	9.825%	$7.3034	$7.30	$7.30	$7.30
Purchase #3	$127.89	7.425%	$137.3858	$137.39	$137.40	$137.40
Purchase #4	$89.82	11.842%	$100.4565	$100.46	$100.45	$100.50
Purchase #5	$176.65	13.269%	$200.0897	$200.09	$200.10	$200.10
Purchase #6	$148.86	9.240%	$162.6147	$162.61	$162.60	$162.60
Purchase #7	$246.99	7.639%	$265.8576	$265.86	$265.85	$265.90
7 purchase totals =	$984.12		$1,081.3229	$1,081.33	$1,081.30	$1,081.40