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	$197.43	13.216%	$223.5223	$223.52	$223.50	$223.50
Purchase #2	$202.91	12.803%	$228.8886	$228.89	$228.90	$228.90
Purchase #3	$66.29	7.606%	$71.332	$71.33	$71.35	$71.30
Purchase #4	$66.62	6.271%	$70.7977	$70.80	$70.80	$70.80
Purchase #5	$143.68	11.859%	$160.719	$160.72	$160.70	$160.70
Purchase #6	$152.87	13.234%	$173.1008	$173.10	$173.10	$173.10
Purchase #7	$108.27	13.702%	$123.1052	$123.11	$123.10	$123.10
7 purchase totals =	$938.07		$1,051.4656	$1,051.47	$1,051.45	$1,051.40