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	$53.72	5.776%	$56.8229	$56.82	$56.80	$56.80
Purchase #2	$26.68	3.333%	$27.5692	$27.57	$27.55	$27.60
Purchase #3	$189.47	5.751%	$200.3664	$200.37	$200.35	$200.40
Purchase #4	$46.85	4.784%	$49.0913	$49.09	$49.10	$49.10
Purchase #5	$171.84	7.843%	$185.3174	$185.32	$185.30	$185.30
Purchase #6	$40.77	7.565%	$43.8543	$43.85	$43.85	$43.90
Purchase #7	$216.54	9.804%	$237.7696	$237.77	$237.75	$237.80
7 purchase totals =	$745.87		$800.7911	$800.79	$800.70	$800.90