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	$86.72	3.318%	$89.5974	$89.60	$89.60	$89.60
Purchase #2	$210.37	3.601%	$217.9454	$217.95	$217.95	$217.90
Purchase #3	$198.43	12.864%	$223.956	$223.96	$223.95	$224.00
Purchase #4	$93.34	4.501%	$97.5412	$97.54	$97.55	$97.50
Purchase #5	$156.46	12.451%	$175.9408	$175.94	$175.95	$175.90
Purchase #6	$225.32	5.769%	$238.3187	$238.32	$238.30	$238.30
Purchase #7	$184.82	13.116%	$209.061	$209.06	$209.05	$209.10
7 purchase totals =	$1,155.46		$1,252.3605	$1,252.37	$1,252.35	$1,252.30