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	$44.41	10.174%	$48.9283	$48.93	$48.95	$48.90
Purchase #2	$118.28	7.816%	$127.5248	$127.52	$127.50	$127.50
Purchase #3	$101.87	13.584%	$115.708	$115.71	$115.70	$115.70
Purchase #4	$98.73	4.600%	$103.2716	$103.27	$103.25	$103.30
Purchase #5	$226.68	6.705%	$241.8789	$241.88	$241.90	$241.90
Purchase #6	$165.54	7.813%	$178.4736	$178.47	$178.45	$178.50
Purchase #7	$105.34	13.370%	$119.424	$119.42	$119.40	$119.40
7 purchase totals =	$860.85		$935.2092	$935.20	$935.15	$935.20