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	$53.62	7.160%	$57.4592	$57.46	$57.45	$57.50
Purchase #2	$90.30	6.399%	$96.0783	$96.08	$96.10	$96.10
Purchase #3	$77.64	11.379%	$86.4747	$86.47	$86.45	$86.50
Purchase #4	$122.92	6.259%	$130.6136	$130.61	$130.60	$130.60
Purchase #5	$69.86	10.713%	$77.3441	$77.34	$77.35	$77.30
Purchase #6	$178.26	11.447%	$198.6654	$198.67	$198.65	$198.70
Purchase #7	$159.89	5.558%	$168.7767	$168.78	$168.80	$168.80
7 purchase totals =	$752.49		$815.4120	$815.41	$815.40	$815.50