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	$196.94	12.261%	$221.0868	$221.09	$221.10	$221.10
Purchase #2	$212.60	4.826%	$222.8601	$222.86	$222.85	$222.90
Purchase #3	$94.76	8.751%	$103.0524	$103.05	$103.05	$103.10
Purchase #4	$54.77	12.524%	$61.6294	$61.63	$61.65	$61.60
Purchase #5	$204.28	4.298%	$213.06	$213.06	$213.05	$213.10
Purchase #6	$86.69	4.280%	$90.4003	$90.40	$90.40	$90.40
Purchase #7	$159.80	11.390%	$178.0012	$178.00	$178.00	$178.00
7 purchase totals =	$1,009.84		$1,090.0902	$1,090.09	$1,090.10	$1,090.20