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	$90.93	13.800%	$103.4783	$103.48	$103.50	$103.50
Purchase #2	$107.37	13.768%	$122.1527	$122.15	$122.15	$122.20
Purchase #3	$99.69	5.407%	$105.0802	$105.08	$105.10	$105.10
Purchase #4	$25.88	5.540%	$27.3138	$27.31	$27.30	$27.30
Purchase #5	$174.56	10.735%	$193.299	$193.30	$193.30	$193.30
Purchase #6	$154.84	4.765%	$162.2181	$162.22	$162.20	$162.20
Purchase #7	$64.43	12.624%	$72.5636	$72.56	$72.55	$72.60
7 purchase totals =	$717.70		$786.1057	$786.10	$786.10	$786.20