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	$105.83	6.836%	$113.0645	$113.06	$113.05	$113.10
Purchase #2	$49.40	9.376%	$54.0317	$54.03	$54.05	$54.00
Purchase #3	$97.31	4.719%	$101.9021	$101.90	$101.90	$101.90
Purchase #4	$175.41	3.734%	$181.9598	$181.96	$181.95	$182.00
Purchase #5	$57.95	13.161%	$65.5768	$65.58	$65.60	$65.60
Purchase #6	$103.64	10.417%	$114.4362	$114.44	$114.45	$114.40
Purchase #7	$198.76	12.392%	$223.3903	$223.39	$223.40	$223.40
7 purchase totals =	$788.30		$854.3614	$854.36	$854.40	$854.40