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	$185.61	3.711%	$192.498	$192.50	$192.50	$192.50
Purchase #2	$54.30	10.405%	$59.9499	$59.95	$59.95	$59.90
Purchase #3	$156.92	6.218%	$166.6773	$166.68	$166.70	$166.70
Purchase #4	$101.36	12.537%	$114.0675	$114.07	$114.05	$114.10
Purchase #5	$164.68	4.231%	$171.6476	$171.65	$171.65	$171.60
Purchase #6	$182.90	10.702%	$202.474	$202.47	$202.45	$202.50
Purchase #7	$147.54	7.467%	$158.5568	$158.56	$158.55	$158.60
7 purchase totals =	$993.31		$1,065.8711	$1,065.88	$1,065.85	$1,065.90