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	$53.69	5.328%	$56.5506	$56.55	$56.55	$56.60
Purchase #2	$103.64	7.690%	$111.6099	$111.61	$111.60	$111.60
Purchase #3	$122.46	7.742%	$131.9409	$131.94	$131.95	$131.90
Purchase #4	$200.55	5.142%	$210.8623	$210.86	$210.85	$210.90
Purchase #5	$239.83	11.661%	$267.7966	$267.80	$267.80	$267.80
Purchase #6	$175.69	11.200%	$195.3673	$195.37	$195.35	$195.40
Purchase #7	$151.27	8.789%	$164.5651	$164.57	$164.55	$164.60
7 purchase totals =	$1,047.13		$1,138.6927	$1,138.70	$1,138.65	$1,138.80