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	$55.77	12.256%	$62.6052	$62.61	$62.60	$62.60
Purchase #2	$185.35	8.216%	$200.5784	$200.58	$200.60	$200.60
Purchase #3	$37.96	10.417%	$41.9143	$41.91	$41.90	$41.90
Purchase #4	$142.72	11.173%	$158.6661	$158.67	$158.65	$158.70
Purchase #5	$177.64	6.597%	$189.3589	$189.36	$189.35	$189.40
Purchase #6	$44.46	11.663%	$49.6454	$49.65	$49.65	$49.60
Purchase #7	$223.49	6.617%	$238.2783	$238.28	$238.30	$238.30
7 purchase totals =	$867.39		$941.0466	$941.06	$941.05	$941.10