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	$152.43	11.340%	$169.7156	$169.72	$169.70	$169.70
Purchase #2	$167.56	10.526%	$185.1974	$185.20	$185.20	$185.20
Purchase #3	$130.67	9.300%	$142.8223	$142.82	$142.80	$142.80
Purchase #4	$164.69	13.330%	$186.6432	$186.64	$186.65	$186.60
Purchase #5	$208.40	7.215%	$223.4361	$223.44	$223.45	$223.40
Purchase #6	$166.89	12.466%	$187.6945	$187.69	$187.70	$187.70
Purchase #7	$171.64	9.211%	$187.4498	$187.45	$187.45	$187.40
7 purchase totals =	$1,162.28		$1,282.9589	$1,282.96	$1,282.95	$1,282.80