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	$58.41	7.370%	$62.7148	$62.71	$62.70	$62.70
Purchase #2	$45.31	13.420%	$51.3906	$51.39	$51.40	$51.40
Purchase #3	$118.88	7.105%	$127.3264	$127.33	$127.35	$127.30
Purchase #4	$180.77	6.114%	$191.8223	$191.82	$191.80	$191.80
Purchase #5	$72.58	11.586%	$80.9891	$80.99	$81.00	$81.00
Purchase #6	$233.65	12.584%	$263.0525	$263.05	$263.05	$263.10
Purchase #7	$9.80	7.461%	$10.5312	$10.53	$10.55	$10.50
7 purchase totals =	$719.40		$787.8269	$787.82	$787.85	$787.80