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	$58.45	6.453%	$62.2218	$62.22	$62.20	$62.20
Purchase #2	$130.56	4.134%	$135.9574	$135.96	$135.95	$136.00
Purchase #3	$178.90	9.732%	$196.3105	$196.31	$196.30	$196.30
Purchase #4	$150.30	4.658%	$157.301	$157.30	$157.30	$157.30
Purchase #5	$98.54	12.679%	$111.0339	$111.03	$111.05	$111.00
Purchase #6	$112.58	9.748%	$123.5543	$123.55	$123.55	$123.60
Purchase #7	$226.62	7.347%	$243.2698	$243.27	$243.25	$243.30
7 purchase totals =	$955.95		$1,029.6487	$1,029.64	$1,029.60	$1,029.70