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	$86.76	5.203%	$91.2741	$91.27	$91.25	$91.30
Purchase #2	$47.79	13.195%	$54.0959	$54.10	$54.10	$54.10
Purchase #3	$36.81	7.824%	$39.69	$39.69	$39.70	$39.70
Purchase #4	$57.83	9.194%	$63.1469	$63.15	$63.15	$63.10
Purchase #5	$129.87	7.307%	$139.3596	$139.36	$139.35	$139.40
Purchase #6	$115.35	10.815%	$127.8251	$127.83	$127.85	$127.80
Purchase #7	$55.79	12.841%	$62.954	$62.95	$62.95	$63.00
7 purchase totals =	$530.20		$578.3456	$578.35	$578.35	$578.40