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	$233.31	4.773%	$244.4459	$244.45	$244.45	$244.40
Purchase #2	$100.72	9.494%	$110.2824	$110.28	$110.30	$110.30
Purchase #3	$241.50	5.566%	$254.9419	$254.94	$254.95	$254.90
Purchase #4	$171.74	8.621%	$186.5457	$186.55	$186.55	$186.50
Purchase #5	$69.35	3.636%	$71.8716	$71.87	$71.85	$71.90
Purchase #6	$190.98	12.651%	$215.1409	$215.14	$215.15	$215.10
Purchase #7	$224.51	13.682%	$255.2275	$255.23	$255.25	$255.20
7 purchase totals =	$1,232.11		$1,338.4559	$1,338.46	$1,338.50	$1,338.30