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	$85.27	7.420%	$91.597	$91.60	$91.60	$91.60
Purchase #2	$243.32	12.482%	$273.6912	$273.69	$273.70	$273.70
Purchase #3	$179.38	9.648%	$196.6866	$196.69	$196.70	$196.70
Purchase #4	$38.45	7.680%	$41.403	$41.40	$41.40	$41.40
Purchase #5	$246.41	11.704%	$275.2498	$275.25	$275.25	$275.20
Purchase #6	$105.66	10.757%	$117.0258	$117.03	$117.05	$117.00
Purchase #7	$55.79	5.403%	$58.8043	$58.80	$58.80	$58.80
7 purchase totals =	$954.28		$1,054.4577	$1,054.46	$1,054.50	$1,054.40