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	$191.88	3.539%	$198.6706	$198.67	$198.65	$198.70
Purchase #2	$240.29	6.150%	$255.0678	$255.07	$255.05	$255.10
Purchase #3	$54.85	11.437%	$61.1232	$61.12	$61.10	$61.10
Purchase #4	$134.67	11.595%	$150.285	$150.29	$150.30	$150.30
Purchase #5	$33.65	10.773%	$37.2751	$37.28	$37.30	$37.30
Purchase #6	$107.26	7.575%	$115.3849	$115.38	$115.40	$115.40
Purchase #7	$143.85	11.771%	$160.7826	$160.78	$160.80	$160.80
7 purchase totals =	$906.45		$978.5892	$978.59	$978.60	$978.70