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	$176.84	7.713%	$190.4797	$190.48	$190.50	$190.50
Purchase #2	$197.67	12.864%	$223.0983	$223.10	$223.10	$223.10
Purchase #3	$64.99	9.482%	$71.1524	$71.15	$71.15	$71.20
Purchase #4	$173.79	11.209%	$193.2701	$193.27	$193.25	$193.30
Purchase #5	$53.55	9.131%	$58.4397	$58.44	$58.45	$58.40
Purchase #6	$177.93	4.277%	$185.5401	$185.54	$185.55	$185.50
Purchase #7	$175.90	11.467%	$196.0705	$196.07	$196.05	$196.10
7 purchase totals =	$1,020.67		$1,118.0508	$1,118.05	$1,118.05	$1,118.10