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	$92.62	13.715%	$105.3228	$105.32	$105.30	$105.30
Purchase #2	$83.87	6.483%	$89.3073	$89.31	$89.30	$89.30
Purchase #3	$72.35	8.581%	$78.5584	$78.56	$78.55	$78.60
Purchase #4	$140.45	9.553%	$153.8672	$153.87	$153.85	$153.90
Purchase #5	$228.78	11.287%	$254.6024	$254.60	$254.60	$254.60
Purchase #6	$206.65	6.518%	$220.1194	$220.12	$220.10	$220.10
Purchase #7	$237.63	13.455%	$269.6031	$269.60	$269.60	$269.60
7 purchase totals =	$1,062.35		$1,171.3806	$1,171.38	$1,171.30	$1,171.40